LONDON (AFP) - Stanislas Wawrinka defeated David Ferrer 6-7 (3/7), 6-4, 6-1 on Friday to keep alive his hopes of making the last four of the ATP World Tour Finals.
But Switzerland's first-time participant in the year-end event will, however, need a victory from Rafael Nadal in a later concluding Group A match over Tomas Berdych.
A Nadal loss would give Berdych a spot in the final four alongside the Spanish world number one.
Wawrinka was pleased with his battling effort against Ferrer in just over two and a quarter hours after throwing away the first set while leading 5-2 but losing in a tiebreaker.
"Sure, tonight I will be a big fan of Rafa," said the winner. "I did my job all week, did the best I could for all three matches.
"Even if Berdych wins, it's been an amazing week for me already. I beat Berdych, number five David Ferrer, I lost a tough one against Nadal. It was quite good level for me, that's the most important.
"I can be only really happy with the tournament. Doesn't matter what's happens tonight." Wawrinka committed a massive 30 unforced errors in the 61-minute first set against the 31-year-old Ferrer.
Even if the Spaniard had nothing to lose, and was out of semi-final contention, he fought like a terrier to keep Wawrinka off-balance in the first set.
"I saw at the beginning that he's not really at his best,"said Wawrinka.
"He's a little bit tired, especially mentally. Every long rally, I had the control of it.
"The important thing was to fight with myself to keep the ball in, to try to stay with him, to show him that I'm gonna play some long rallies, that I'm going to try to be aggressive, but not rushing too much.
"That's what I did better at the end and it made a big difference today.
"I was showing him that I'm gonna be there and I'm gonna improve my game if I can, I'm gonna fight on every ball. That if he wants to beat me, he has to really find the way to beat me." Ferrer rallied from the depths, breaking in the ninth game and again in the 11th for 6-5 after the Swiss saved four break points.
But a break-back from Wawrinka levelled at six apiece to bring on the decider.
Ferrer sprinted to 3-1 and eventually took the set to Wawrinka's dismay from a Swiss forehand error.
Wawrinka came back in the second with an early break which was enough to see him through to one set each.
In the third set, the Swiss sensed the finishing line and earned two breaks to bolt home after conversions on six of seven break points.
He struck 35 winners and overcame 56 unforced errors.
Nadal takes a 16-3 record over Berdych into their match, having won the pair's last 15 meetings.