Mark Clattenburg refereed in the Premier League for 13 years between 2004 and 2017.
During that time, he also took charge of countless Champions League and Europa League games, as well as international fixtures.
He'll have plenty of special memories after mixing with some of the biggest footballers on the planet for well over a decade, but it wasn't all fun and games.
At the top level, things get very competitive and more often than not when there's so much on the line, things can boil over.
Some players are notorious for being 'hotheads' on the pitch, often making things very difficult for referees.
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Now he's stepped down from working in the Premier League and in UEFA competitions, Clattenburg has revealed five of the worst footballers he ever had to officiate during his career.
Perhaps unsurprisingly, Roy Keane is one, while the English ref also named Jens Lehmann, Pepe, Rio Ferdinand and Craig Bellamy as some of the hardest players to deal with.
"I used to find Jens Lehmann such hard work. He was always difficult because he’d always whinge about people stepping on his toes in the penalty area," Clattenburg told The Sun.
"I found Ferdinand difficult to referee during that Fergie era because he was always trying to play mind games."
Ex-Real Madrid defender Pepe is the only non-Premier League player on his list - but Clattenburg explained his reasons for that, before explaining why Keane is also on the list:
"Pepe was a guy who was always difficult because he’d try to frame stuff and wind attackers up to get them sent off, which is not always a great thing when you’re trying to referee a football match.
"Roy was physical, hard and you couldn’t trust him. Look at the tackle on Alf-Inge Haaland for example. You never knew what he was going to do next."
Interestingly, the Manchester United midfielder wasn't the worst Clattenburg had to deal with - that honour goes to Bellamy instead.
"The worst one - and I’ve thought it for years - was Bellamy. He was just the most irritating player on the pitch - and he was irritating off it," the 44-year-old concluded.
With all the stories we've heard over the years about the Welshman, it's not hard to believe that he was a nightmare to referee every week.News Now - Sport News