London — Roger Federer entered this year's Wimbledon quarter-finals with a 4-0 head-to-head lead against Kevin Anderson, having never lost a set against the South African.
There the eight-time Wimbledon winner won the first two sets and earned a match point in the third set, before Anderson battled back and eventually triumphed 13-11 in the fifth set.
Federer will have a chance to avenge that defeat on Thursday at the ATP Finals, as he pushes to reach the semi-finals at the season finale for the 15th time.
But the 37-year-old says that Wimbledon match won't be the first thing on his mind when he steps on court against Anderson.
"I don't think I'll go into the match thinking too much of it. I think I have enough things to focus on from my own side, from my own game, to make sure I play a good match against him here in the next match," Federer said.
"I'm really excited to get a chance to play him again, to be honest. I've played well against him in the past. I hope I can reproduce something like that."
Anderson, perhaps, has never played better tennis.
The South African is 2-0 in Group Lleyton Hewitt in his debut at the ATP Finals, so Federer knows he must bring his best to stand a chance.
"I could win and still not make it, so from that standpoint it's not in my power. That's okay. If I don't pass, I don't pass, and I deserve not to pass. (What is) important for me is to play a good last match here in the round-robin, try to beat Kevin," Federer said.
"He has been playing great. He has had a wonderful season. Played great against me as well at Wimbledon... I can't talk about what would come next because it's a hard match in itself."
In his first two matches at The O2, Anderson lost only a combined 10 games, dropping just one game against Kei Nishikori on Tuesday.
So the fourth seed will take plenty of confidence into his match against Federer.
"I'm looking forward to playing Roger," Anderson said. "It is always a great challenge taking him on, on the court. It's a great opportunity, up against arguably the best player of all time. I feel like I've played two really good matches, so definitely excited to come back and play him."
Also in action will be Austria's Dominic Thiem and Nishikori. Thiem lost his first two matches in round-robin play and will have to defeat the Japanese star in straight sets to stand any chance of advancing to the semi-finals.
"First of all, I have to get my tennis back. I'll try that. If I don't get it back, I don't need to watch for the other results because then I will also lose my third match. I have to get my good tennis back," Thiem said. "I really want to play a good match. Doesn't matter if it's the last one here or not."
Nishikori has won three of the pair's four head-to-head meetings, including a victory just weeks ago at Thiem's home tournament, the Vienna Open.
There, Nishikori took just 68 minutes to eliminate Thiem 6-3, 6-1.
"It's a different surface. This one is much quicker," Nishikori said. "He's obviously a good player. He has done really well this year. So, I'm sure it's going to be a tough one. I've got to play, I have to raise my level for sure."