Canada's Milos Raonic qualified for the semi-finals of the ATP World Tour Finals with a 7-6 (5), 6-3 win over Dominic Thiem on Thursday.
Raonic fired 14 aces in the match to advance to the semi-finals of the marquee tennis event for the first time in his career.
The fourth-ranked player, from Thornhill, Ont., never faced break point, and converted two of six break opportunities against his eighth-ranked opponent from Austria.
Raonic finished 2-1 in round-robin play and second in the Ivan Lendl group. He'll play the winner of the John McEnroe group, which world No. 1 Andy Murray currently leads with a 2-0 record.
"I stepped up when I had an opportunity in the tiebreak. I stepped up at the beginning of the second set and the end of it," said Raonic, who reached the Wimbledon final this year but lost to Murray. "There's a lot definitely to be proud of, playing under that kind of pressure."
Raonic also said he got some tips this week from John McEnroe, who worked with the Canadian during the grass-court season.
"He shares a lot of wisdom with me, a lot of his opinions. I respect that," Raonic said. "It was a big plus to have him there."
Earlier, No. 2 Novak Djokovic downed David Goffin 6-1, 6-2 to advance to the semis and finish group play undefeated for the fourth time in the past five years.
Djokovic is playing for a lot more than just a record-tying sixth title at the ATP finals. The second-ranked Serb is also looking to reclaim the No. 1 ranking. But there are more matches to play before the 12-time Grand Slam champion can be assured of finishing another season as the top-ranked player.
"Everything has been going … in a positive direction. I've been playing better and better as I proceed in the tournament," Djokovic said.
Murray took over the No. 1 ranking from Djokovic this month at the Paris Masters, but if Djokovic does better than Murray this weekend at the ATP finals, he will jump back ahead and finish the season on top for the third straight season and the fifth time in six years.
"That's something you wish for, to have everything in your hands, not to depend on other players," Djokovic said. "In this particular case, I'm glad it's like that."
Murray, meanwhile, is looking to extend his stay at the top through the off-season for the first time. He plays his third group match on Friday against U.S. Open champion Stan Wawrinka.
Goffin was making his debut at the tournament on Thursday, filling in for the injured Gael Monfils.
The 11th-ranked Belgian didn't get much chance against Djokovic, earning only one break point – and that in the final game of the match. Djokovic, meanwhile, converted four of his six break points, two in each set.
"It was not easy," said Goffin, an alternate who found out on Wednesday he would be facing Djokovic. "I didn't feel really well. I didn't feel the rhythm. My groundstrokes, my best weapons, were not there. It's not easy against Novak when it's like that."
Djokovic is a five-time champion at the eight-man finals. He has won 21 of his last 22 matches at the O2 since 2012, including four straight titles. He also won the title in 2008, when the tournament was in Shanghai, so another victory on Sunday will put him even with Roger Federer as six-time champions.
Djokovic opened the match against Goffin with two double-faults, but he didn't do much wrong after that. He ended up winning 83 per cent of the points on his first serve, even with four double-faults in the first set.
Another match won, but more work ahead.
"I always try to really take the last drop of energy, whatever is left in my body, to perform as well as I can," Djokovic said, "and finish off the season in the best possible way."