Nadal victory sends Wawrinka through to World Tour Finals semis
Rafael Nadal beat Tomas Berdych to send debutant Stanislas Wawrinka through to the semi-finals of the Barclays ATP World Tour Finals in London.
Wawrinka had earlier beaten David Ferrer but victory for Berdych would have eliminated the Swiss despite two round-robin triumphs.
He might have been quietly confident given Nadal had beaten Berdych in their last 15 matches dating back to 2006, but the Czech put up a very good fight before a late collapse to lose 6-4 1-6 6-3.
Wawrinka will play Group B winner Novak Djokovic in the semi-finals on Sunday while Nadal, who made it three wins from three matches, will meet the winner of Saturday's match between Roger Federer and Juan Martin del Potro.
Wawrinka would have been sitting quite comfortably during a first set in which Nadal broke in the opening game and was never threatened.
Berdych kept the deficit to one break with fine serving but Nadal was equally dominant on serve and his formidable forehand was in sparkling form.
It all changed early in the second set, though, Berdych breaking for 2-0 when a stinging return forced the error on Nadal's forehand.
And remarkably after five games of the set the world number one had managed only four points.
He held to force Berdych to serve it out, and the fifth seed recovered from 0-30 before clinching it with an ace.
The third set was extremely tight until the eighth game, when Berdych decisively cracked.
Having served so well, he threw in two double faults to be broken and Nadal clinched victory on his second match point with his 17th forehand winner of the match.
Wawrinka had to battle extremely hard to keep his hopes alive in the afternoon match, recovering from a set down to defeat already-eliminated David Ferrer 6-7 (3/7) 6-4 6-1.
The Swiss let a 5-2 lead slip away in the first set and Ferrer was much more solid in the tie-break.
Wawrinka withstood more pressure at the start of the second set, and the match turned around when he broke for a 2-1 lead, Ferrer taking his frustration out on his racquet.
The seventh seed dominated the decider and then insisted he was happy with his tournament whether he made the semi-finals or not.
The Swiss said: "Even if Berdych wins against Rafa, it's an amazing week for me already. I had to win against Tomas Berdych, the number five, David Ferrer, I lost a tough one against Nadal.
"At the ATP World Tour Finals, it was quite a good level for me. That's the most important thing. I can be only really be happy with the tournament."
The 28-year-old is a fan of the round-robin format because of the unique challenge it presents.
He said: "It's always strange, but that's part of the tournament. That's what makes it different. I quite like it."
Ferrer has had a fine year, reaching his first grand slam final at the French Open, and he is currently at a career-high ranking of number three.
But he has played for seven weeks in a row across Asia and Europe and he conceded his schedule made it virtually impossible to perform at his best in London.
The 31-year-old said: "I made the final in Stockholm, the final in Valencia, the final in Paris, and three matches here. It's too much. But now I know it's too much. Before, I didn't know it."