North Queensland Cowboys co-captain Johnathan Thurston has had enough. It's an hour into a rugby league game at Sydney's Parramatta Stadium one Friday evening in June and Thurston's team is menacing Parramatta's defensive line when they make a mistake, which prompts tall, muscular referee Ben Cummins to blow his whistle in favour of the home side. Thurston explodes. His team is down six points to 18 before a stridently partisan crowd of 10,142 seething Eels supporters. Beneath his trademark white headgear, the Cowboys captain is viciously mouthing off at the official. He, too, has had enough, and raises both hands skyward as a signal to stop the clock.

"Okay, Johnathan," begins Cummins, in a measured tone not dissimilar to a headmaster disciplining an unruly pupil. He states his reason for the stoppage: "It's the way you're talking." Thurston is furious. He's not listening. His ears are shut but his mouth continues firing. The crowd responds to this conflict between match official and enemy captain by jeering enthusiastically; their team is winning and Thurston is losing his head. The ref has heard enough.

"Johnathan, I'm talking here," Cummins says. "It's the way you're talking to me. Talk like that again and I'll penalise you."

Having poured cold water on Thurston's fire, Cummins blows his whistle and the game continues.

In the tunnel between team dressing rooms prior to kick-off, it was a different story. Cummins met Thurston and Eels captain Jarryd Hayne for the ritual coin toss. The trio traded easy smiles and handshakes. After the referee introduced me to Thurston, I asked the Cowboys captain whether he's a Ben Cummins fan. His reply came with a laugh: "I'm a referee fan, mate!"

Prior to the Parramatta game, I meet former NRL official Tim Mander at his office in Everton Park, in Brisbane's inner-north. Mander, 52, called time on his on-field role in 2005, then worked part-time as a video referee for another six years. He is now the Member for Everton and Queensland's Minister for Housing and Public Works. A framed photograph of a referee sin-binning Queensland league legend Wally Lewis is mounted on his wall.

"I was involved with first-grade football for more than 20 years," says Mander. "Every year, the same story would break, that the referees were 'in crisis'. [The National Rugby League] has done everything you could possibly do to improve refereeing standards." He counts them off on his fingers: they became full-time professionals, they adopted two referees per match, and they introduced the video replay system, among other changes. "What else can they possibly do?" he asks. "They can't do anything else. The issue is that, unfortunately, the selection of referees is contained to people of the human race."

Few of us hold jobs in which our momentary lapses in concentration take place before televised audiences numbering into the millions. A mistake made by a referee can shift a sporting world on its axis; a decision to award a penalty or not in the final moments of a tight contest can end careers - of players, coaches and staff. It takes a certain kind of mind to embrace this role with confidence.

As kick-off approaches at Parramatta Stadium, Cummins - a primary school physical education teacher who enjoys any chance to return to the classroom should his schedule permit - changes into his pink uniform and weighs himself. He's 89 kilograms, but will drop two kilos in the ensuing 80 minutes. Every top-level sports official is a picture of health; NRL referees run nine kilometres each match, on average, while their AFL counterparts run 12.

At the age of 40, Cummins looks strong and fit enough to be running with either team tonight, as does his slightly shorter assistant, Gavin Reynolds. The referees' dressing room is a cosy four-by-five-metre box that contains an adjoining room with showers and a massage table. The jocular mood in the room belies the seriousness of the role; after all, there is security posted outside the door, and they'll be accompanied to their cars at night's end.

"It's a requirement that we're escorted back to our cars," says Cummins. "Generally, nothing happens. There are some games where the crowd gets quite heated, and you make sure you have security. If you give the game 30 to 60 minutes, most people have headed off by then. Most people take out their frustrations on forums or social media these days."

Upstairs at Parramatta Stadium, Shayne Hayne has just finished evaluating the curtain-raising Holden Cup under-20s match from the video referee's box. He and Cummins shared referee duties at the year's first two State of Origin matches. "I try not to worry too much about public perception," says Hayne in the hallway, as Wally Lewis and TV caller Ray Hadley bustle past. "Sometimes perception is reality, but 90 per cent of the time it's agenda-driven. I tell young refs to stay away from reading the papers. It can play with your head."

Hayne is tall, tanned and one of the league's most experienced officials, having refereed more than 300 NRL games since his debut in 2001. The 46-year-old's current annual contract is worth $160,000, with match payment bonuses awarded for his involvement in State of Origin games ($4000 apiece), Test matches and semi-finals ($3500 each) and grand finals ($6000), the latter of which Hayne has officiated three times (2009, 2010 and 2013). All 20 full-time NRL referees are based in Sydney, and meet four days a week at Olympic Park to train, review their performances and self-analyse. Tuesday is their only day off.

As Cummins blows the whistle downstairs to signal the start of the Eels-Cowboys match, I ask Hayne how he processes the knowledge of making a wrong call on the pitch. "You've got to black-box it, or it compounds," he says. "Two wrongs don't make a right. If you make a mistake, your goal is to get through the next set of six tackles without making another. And then the next two or three minutes." How? "It's about mental toughness," he says, pressing his right middle finger to his temple. "It's all up here."

A game of AFL can't start without the seemingly simple act of smashing a red Sherrin into the grass so it rebounds a good eight metres into the air. "Let's have a nice little game of footy, guys," says Simon Meredith to the Brisbane Lions and Essendon Bombers players crowding the centre circle moments prior to the first bounce at the Gabba in mid-May. He exhales sharply, executes the task perfectly, then scuttles backwards to let the ruckmen contest the ball.

Meredith, a tall, spiky-haired 39-year-old, runs an IT business during the week, yet since his Australian Football League umpiring debut in 2004 he has undertaken the weekend ritual of venturing out into modern-day colosseums and voluntarily subjecting himself to abuse from both sides of a stadium filled with sports maniacs. On this Saturday night there are 26,432 people here watching his every move, not to mention dozens of cameras trained on him, beaming to another 215,000 pay-TV viewers. He's wearing a communications vest that's miked-up and recording everything he says, while an AFL official sits high in the stands, tracking his every move in exacting detail, including whether that Sherrin's bounce is "straight, offline, or badly offline".

A badly offline bounce results in a recall, wherein the umpire sheepishly tosses the ball above his head rather than attempting a second bounce. Meredith and his colleague, Andrew Mitchell, both yield recalls in the first quarter tonight; keen home viewers will hear Mitchell's sincere apology to the players crowding the middle circle. "Sorry, guys," he says before lobbing the ball skyward and taking several backward steps.

For Meredith, having umpired the league's last two grand finals means this particular game is likely to be but a footnote in his career of more than 200 AFL games. The stakes this evening might be higher, but the fundamentals of his role are the same as when, aged 16, he began umpiring under-18s VFL games, earning $40 a match (a part-time job more enjoyable, and healthier, than flipping burgers like his friends). Today, an elite AFL field umpire earns between $70,000 and $150,000 a year, but the essence of watching play, making decisions and blowing the whistle remain the same.

Matthew Leppard completes the trio of field umpires officiating tonight. They each take turns patrolling one of three zones on the field, the most taxing is the centre - whoever occupies the middle when a goal is kicked is tasked with the dreaded centre bounce. While the game plays out, 31-year-old "emergency" umpire Sam Hay watches from the sideline, anticipating the possibility that one of his colleagues might succumb to a rare injury or circumstance that requires his substitution.

Hay is wearing black trackpants and a lime-green shirt. In 2010, the AFL established its sense of humour by signing a sponsorship deal wherein one of the country's largest eyesight specialists was allowed to stitch its name into those shirts. A Facebook group named "Even though AFL umpires are sponsored by OPSM, they still can't see" soon emerged, attracting almost 22,000 followers.

Four hours before first bounce, in the lobby of a central Brisbane hotel, Andrew Mitchell shows me one of his preparation techniques: pocket-sized printed lists of today's squads, including guernsey numbers and names. "I'll get their attention more quickly if I can refer to them by their name instead of their number," says the 32-year-old.

Of the four field umpires, Mitchell strikes me as the most serious: in a maxi-taxi to the stadium, he's engrossed in watching a live Port Adelaide versus Fremantle game on his smartphone, earbuds wedged in to catch the commentary while boundary umpire Mark Thomson watches over his shoulder. "A lot of umpires are pretty calm in normal life," says Leppard, who is 31 and slightly built. "I'm an introvert; most of us are. We're calm, methodical thinkers." Off the pitch, Leppard works for ANZ as a credit risk analyst, Mitchell is a tax accountant, and Hay is a personal trainer.

"There's enough money in umpiring that I don't need the day job," says Leppard while tying his shoelaces in the umpires' dressing room at the Gabba. "I earn more from this than at ANZ."

But, like the players with whom they share the pitch, officials are only one nasty injury away from early retirement. This means many of these men have decided that it's best to draw an income from life outside of the game, rather than putting all their eggs in one basket. "The work-life balance is tough," Leppard says. "I have two full-time jobs: when I'm not working, I'm umpiring."

Twice a week, all of the AFL's Melbourne-based field umpires train together; their strength, running and recovery programs are overseen by four full-time coaches. They watch footage, write critiques of their own performances and rate themselves on a scale from "very good" to "poor". The workload for each of the league's 33 field umpires is significant, and that's without considering external pressures placed on them by analytical sports journalists and one-eyed spectators who'll loudly criticise any decision that goes against their team.

"Most fans don't appreciate the amount of work we put in," says Mitchell without a trace of self-pity, before heading out onto the pitch to practise his centre bounce with his colleagues. "We're effectively like another playing team; our performance means as much to us as the players' does to them."

Of the four Australian football codes, the A-League is the baby: next season the competition turns 10, and while attendance and viewing rates are growing, it's still a distant fourth to the NRL, AFL and Super Rugby. Accordingly, none of the A-League's 13 referees occupies a full-time, salaried role; instead, they each receive a match payment of $1400 a game.

"It's quite funny when you're in front of 40,000 people one day, refereeing the Melbourne derby; then you have to catch a 6am flight the next day, go straight to work and put in another eight hours," says Strebre Delovski. "It's pretty difficult, but it's something that we have to do, unfortunately. It's not that glamorous."

Delovski works in Sydney as an accounts supervisor for the Master Builders Association. Twice a week, he meets with the local A-League, Youth League and W-League referees for group training at Blacktown International Sportspark, while elsewhere in the week he gives up two of his lunch breaks to train at the University of Sydney, next to his workplace.

In January, the bald 38-year-old became the fourth A-League referee to adjudicate 100 matches. He's also one of a handful of Australian referees accredited by the global football body FIFA, which means that he's occasionally assigned to control international friendly matches. "As a whole, all referees support each other," he says. "For the FIFA guys who travel away together a lot, you've got to have that friendship to stay sane. We have a laugh, and pay each other out; when we're down, we get a lot of messages saying, 'Head up, move on.' "

More than a few such messages were sent Delovski's way following a semi-final game between Brisbane Roar and Melbourne Victory in late April. In the closing minutes, with the home team up 1-0 before 28,350 orange-clad fans, Roar captain Matt Smith brought down his Victory counterpart Mark Milligan in the penalty area. Delovski had a clear view of the incident while standing outside the box, and began raising the whistle toward his lips to signal a spot-kick that would have offered Melbourne the chance to draw scores level. Suddenly, he changed his mind and allowed play to continue. Victory coach Kevin Muscat was livid, and angrily confronted Delovski as he walked off the pitch; Fox Sports commentator Mark Bosnich described it as "the most ridiculous decision I've seen throughout the season".

Remarkably, two days later, the referee told radio station SEN that his hesitation was misplaced. "In hindsight, if I had it again, it's definitely a penalty," he said. "I had a decision to make; unfortunately, it was the incorrect decision." While this admission was heartening, it didn't console sour Victory fans. "I don't see any reason for referees to hide behind their mistakes," Delovski tells me. "In the space of 12 minutes [on air], people changed from wanting blood to saying, 'He's human - move on.' Like players and like coaches, referees make mistakes."

The Super Rugby game that I attend in mid-May sees the hapless Queensland Reds host the Melbourne Rebels at Brisbane's Suncorp Stadium. Prior to kick-off, I meet with video match official (VMO) Steve Leszczynski, a trim, 34-year-old primary school teacher who has occupied this role since 2007 and earns $600 per game.

"Our job used to be try-based; the players crossing the five-metre line was the trigger for us to pay close attention," he tells me as we gaze down at the empty field from a vantage point that neighbours ABC Radio's broadcast booth. "Now we're looking at foul play, injuries and off-the-ball incidents as well. We can refer things that the boys on the field didn't see."

Things such as Reds lock Ed O'Donoghue pushing his hands near the eyes of Rebels captain Scott Higginbotham as the pair scuffle in back-play during the game's final moments, while 42-year-old referee Steve Walsh is otherwise occupied. The Reds are about to throw a line-out at the other end of the pitch when Leszczynski's voice crackles in Walsh's ear. A rigorous discussion between the pair is overheard by the 86,000 fans watching on pay-TV at home, while the VMO replays footage on the big screens. Walsh awards a red card to the Reds player for eye-gouging and a late penalty is gifted to the Rebels, who win the game 30-27. (To compound the controversy, the eye-gouging charge is later overturned by a judicial hearing and the red card is stripped from O'Donoghue's record.)

Unsurprisingly, the officials are showered with boos and jeers by 23,820 furious Reds supporters as they leave the pitch. "Once again we were robbed by a stupid refereeing decision," says Reds captain James Horwill with a rueful shake of his head in a pitchside TV interview, neatly avoiding the fact that his teammate gave away the penalty that cost them the match. It's much easier to blame a third party for your team's failings than face some hard truths closer to home, and for professional athletes, referees remain the ideal proxy for such blame-shifting. (Horwill was later fined $2500 for his comment.)

In the dressing room immediately afterwards, Walsh - an intense, bearded character who, at 188 centimetres and 94 kilos, could easily pass for a rugby union player - says that, as he left the pitch, "I knew what was about to come. I just kept my head down, jogged off and got out of there." He didn't make eye contact with any of the angry Reds supporters leering at him. "I don't inflame people," Walsh says. "There's nothing to be gained from engaging with them."

Leszczynski jokes that his life flashed before his eyes before he pressed the button to trigger the eye-gouge discussion. His sweaty, spent colleagues tuck into fruit, sandwiches and sports drinks while agreeing that Leszczynski made the right call.

It's not ideal to end a close match in such contentious circumstances, but that's the nature of their job: to react accordingly to the unpredictable nature of the game. To make correct decisions as often as possible, and to black-box any mistakes for later reflection and self-improvement.

After the match, Steve Walsh - the only salaried rugby union referee in Australia, earning about $150,000 a year - twists his left inner forearm to show me a bold tattoo he had inked on himself after being fired by the New Zealand Rugby Union for "drinking and drugging" in 2009. These seven words are as applicable to life itself as they are to sport: "He who controls himself controls the game."