Roger Federer got back on track with a 7-6(2) 6-3 defeat of Italian Matteo Berrettini on Tuesday and immediately set his sights on a crunch clash with Novak Djokovic that will decide his ATP Finals fate.
Defeat by Austrian Dominic Thiem in his opening round-robin match on Sunday has left the 20-time Grand Slam champion facing only his second group stage exit in 17 appearances at the year-ender.
He repaired some of the damage with an emphatic victory over Italian debutant Berrettini, but will likely need to beat Djokovic to avoid falling before the semi-finals of a tournament he has won a record six times.
Their 49th meeting will take place on Thursday and will be their first clash since Djokovic beat Federer in July's epic Wimbledon final — in which the Swiss held two match points before losing a fifth-set tiebreak.
"We'll find out, but I think it's all flushed away from my side. A lot of water has gone under the bridge since then," Federer said when asked if the memory of that Centre Court defeat was still a bitter one.
"I think we both can take away some confidence from the match. Him obviously a lot. Me maybe a tad bit less.
"But at the end of the day, I didn't hope I was never going to play him again. Actually, it's good for me to play him again, and maybe that all helps to get a chance to get him back or whatever it is. Personally, excited to play Novak on Thursday."
Federer looked far sharper than he did against Thiem although the powerful Italian pushed him hard.
Once Federer won 10 of 11 points to win the first-set tiebreak and break to love at the start of the second, he never looked like suffering another defeat.
Incredibly Federer is now 17-0 in second round-robin matches at the tournament.
The 23-year-old Berrettini was also coming off a heavy defeat by Djokovic in his first appearance at the event, and he showed why he has made such an impact this year.
Berrettini, the first Italian to qualify for the tournament since 1978, had three break points in the eighth game of the second set but Federer served his way out of trouble and the 38-year-old Swiss then broke to claim victory.
After being thrashed by Federer at Wimbledon this year, afterwards calling it a tennis lesson, Berrettini was far happier with their second meeting.
"Today I was more ready. I knew what I had to do to win, to try to win the match," he said.
Djokovic, who is bidding to equal Federer's record of six titles and claim back the world number one ranking from Rafael Nadal, faces Thiem later on Tuesday at the O2 Arena.