Roger Federer clinched a place in the semi-finals of the ATP Tour Finals on Thursday as the defending champion ground out a 6-4 7-6 (7-5) win over Spain's David Ferrer at London's O2 Arena.
Federer required a straight sets win over the fourth seed to seal his spot in the last four with one Group B match to spare and he reached that goal despite a scrappy performance that included 39 unforced errors.
In the day's other game Argentina's Juan Martin del Potro crushed Serbian eighth seed Janko Tipsarevic 6-0 6-4 to keep alive his hopes of securing a place in the semi-finals.
While Federer was some way from his best, the world No.2 displayed his priceless knack of elevating his game on the big points as the 31-year-old extended his winning run at the Tour Finals to 12 matches.
As well as securing his semi-final berth, Federer also achieved a notable personal landmark by recording his 70th match win of the year -- the first time he has done that since he was at the very peak of his form in 2006.
It was a familiar story for Ferrer, who has now lost all 14 of his meetings with Federer, and the Spaniard will need a victory over Janko Tipsarevic in his final match on Saturday to have any chance of qualifying for the semi-finals.
"It was a long match and I'm extremely happy to win," Federer said. "I played a great match. I've qualified and I'm obviously relieved and thrilled that that's the case.
"David's been on a great run and he is so respected by his fellow competitors. I enjoy playing against him, not because I've got a good record, but because he's a great guy and a great competitor."
Meanwhile former US Open champion del Potro took out his must win encounter, blowing Tipsarevic off the court in just one hour and 16 minutes.
The Argentine still needs a win against Federer in his final group match on Saturday to reach the last four and even that may not be enough depending on the result of Ferrer's meeting with Tipsarevic.
At least del Potro still has a chance, unlike Tipsarevic who is destined to crash out after losing both his matches without even winning a set.
"I have a high step up against Federer on Saturday but I will try to beat him," Del Potro said.
"I have worked a lot every day to be here after my injury problems. I'm back in the top 10 and I really want to enjoy this week."
Only Federer, Novak Djokovic and Ferrer have amassed more than del Potro's career-high total of 65 match wins this year and, with recent titles in Basle and Vienna on his CV, he is clearly determined to finish the year on a high.