Federer, 36, is used to playing at peak times of tournaments to guarantee TV viewers and packed stadiums.
At the O2 in London Federer has played at 2pm on Sunday – the opening match – and 8pm on Tuesday.
Supporters were expected his final group game on Thursday also to be at 8pm when he takes on Marin Cilic.
But the ATP yesterday announced he would be playing at 2pm instead – and fans aren’t happy.
They have taken to Twitter to express their displeasure with one writing: “Why did they have to put Federer on in the afternoon tomorrow? Was gonna go if he was on in the evening.”
Another said: “Last time I ever buy evening tickets in advance at the o2. Yet again the absolute imbeciles who decide the draw put the GOAT Federer on in the afternoon to cater for the well off/retirees when everyone else who works is left with Mr Sock. Money down the drain #ATPWorldTourFinals.”
While a fellow fan said: “Absolute b***ocks.”
Roger Federer will play at the ATP Finals in the afternoon session
ATP World Tour Finals odds: Who will win at the O2?
Tue, November 14, 2017
Express Sport runs through the odds for the ATP World Tour Finals at the O2 Arena (Odds provided by Sky Bet, accurate as of 14/11/17)
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Who is favourite to win the ATP World Tour Finals at the O2 Arena?
Federer is certain to move into this tournament's semi-finals, even before his final group match against Cilic.
Alexander Zverev faces American Jack Sock for the second qualifying spot with that clash starting later.
Federer hailed Zverev after beating the German up-and-comer to book his place in the last four of the ATP Finals.
"What I like about Zverev is he's got the full package," Federer said.
"He's already three in the world. I think he's going to leave the World Tour Finals, regardless if he qualifies for the semis or not, with a lot of information.
"I think the last six months of the season gave him everything he needs to work forward to. Then, of course, he's only going to get stronger from here. That should be very encouraging for him and his team."
Fans were annoyed at the decision to put Roger Federer on in the afternoon
Federer remains the favourite to claim a record-stretching seventh title here, even more so after Rafael Nadal became the latest top player to pull out on Monday.
Nadal joins Andy Murray, Novak Djokovic, Stan Wawrinka, Kei Nishikori and Milos Raonic on the sidelines but Federer believes the game's injury epidemic simply comes down to age.
"A lot of the guys are just touching 30 plus," Federer said.
"Back in the day, at 30, a lot of guys were retiring – (Stefan) Edberg, (Pete) Sampras – it was like normal at 29 to 32, to start looking towards the end of your career.
"Now people expect everybody to play till 36 and when somebody is injured at 31, it's like, 'Oh, my God, how is this possible?' Actually, it's a normal thing."