Andy Murray kept hold of the No. 1 ranking for at least another day.
The Wimbledon champion qualified for the semi-finals of the ATP World Tour Finals on Friday by beating Stan Wawrinka 6-4, 6-2.
Murray, who needs to do better than Novak Djokovic this weekend to finish the season as the top-ranked player, broke Wawrinka late in the first set and twice at the start of the second.
"I feel like my game is in a good place," Murray said. "Played much better today than I did a couple days ago. Physically I feel good. So looking forward to the weekend."
Murray took over the No. 1 ranking at the Paris Masters this month, but Djokovic can grab it back if the second-ranked Serbian does better at the season-ending tournament. Djokovic has already qualified for the semi-finals.
Murray will next face Milos Raonic of Thornhill, Ont., on Saturday, while Djokovic meets Kei Nishikori.
"[Raonic] obviously serves big, goes for his shots. He moves forward when he has the chance. I think he probably likes the conditions here. It's a little bit quicker," Murray said. "You don't normally get loads of opportunities against the big servers. Then it comes down to when you do get those chances, whether you take them or not."
Murray's winning streak equals his run earlier this year. Two more victories would deliver his maiden ATP World Tour Finals title while depriving Djokovic of a sixth, and the season-ending top spot.
First, he must get past Raonic for the third time in a major clash in London this year, having beaten him in the final at both Queen's Club and Wimbledon in the summer.
"I'm certainly not taking anything for granted. I know it will be hard," said Murray whose brilliant late-season run has landed him four consecutive titles.
"I've created a few opportunities in the matches. When they've come, I've been pretty clinical," Murray said. "I'll need to be the same tomorrow if I want to win."
Round robin play concluded later as already-eliminated Croatian Marin Cilic warmed up for next week's Davis Cup final against Argentina by beating a tiring Nishikori 3-6, 6-2, 6-3.
It was his first win in six matches at the tournament and the 200 ranking points he earned means he will move above Gael Monfils to a career-high six.
In an early match at O2 Arena, Murray's brother, Jamie, ensured he will finish the year the as the top-ranked doubles player, along with partner Bruno Soares.
"Regardless of what happens over the weekend, we can look back on this year and be very proud of what we've done as a family," Andy Murray said.