Friday, November 26, 2010 Updated: November 27, 1:32 PM ET
Rafael Nadal, Novak Djokovic win
LONDON -- Rafael Nadal and Novak Djokovic completed the semifinal lineup at the ATP World Tour Finals with straight-sets victories Friday.
Rafael Nadal argued with the chair umpire in the first set, but regained his cool and won his match with Tomas Berdych.
The top-ranked Nadal beat Tomas Berdych 7-6 (3), 6-1 in the early match to leave Djokovic needing only one set to finish second in Group A, and the third-seeded Serb defeated a listless Andy Roddick 6-2, 6-3.
Nadal will meet Andy Murray in Saturday's opening semifinal as he bids for his first title at the end-of-season tournament. Djokovic plays Roger Federer.
Roddick began his match against Djokovic with an outside chance of reaching the semifinals but the eighth-ranked American was never in contention and was broken three times in a 65-minute loss.
Nadal, meanwhile, finished Group A with a 3-0 record and finally appears to be getting to grips with the surface at the O2 Arena, having lost all three matches on the same court last year.
"[To] finish the season winning all the matches in the group, three victories against top eight players in probably the most difficult surface for me, is unbelievable now," Nadal said after beating Berdych for the eighth straight time. "I'm very happy how I am playing, how I improved during the tournament."
It wasn't all smooth sailing for Nadal, who lost his cool momentarily and argued furiously with the officials in the first set.
With Nadal trailing 6-5, Berdych's backhand was called out by Brazilian umpire Carlos Bernardes, but Nadal had returned the ball in play. Berdych challenged the call, which confirmed the ball was actually in. The Czech player was then awarded the point.
Nadal was convinced the point should have been replayed and ranted first at Bernardes and then at the tournament supervisor sitting in the front row of the crowd, to no avail.
"There is no argument," Nadal said. "I am right, but it's [a] mistake for him. But he is a great umpire and everybody [makes] a mistake."
Berdych said he thought Nadal had already stopped playing to indicate the ball was out and that the umpire was correct to give him the point.
"The referee is probably scared of him and just let him to talk with him too long," Berdych said. "He was able to play. But every time when you just raise your hand, that means that you stop the play."
The rare outburst only seemed to fire Nadal up. He eventually returned to the baseline to serve at 15-30, and when a fierce forehand drew an error from Berdych, he pumped his fist and yelled his approval.
"Doesn't change nothing, that point," Nadal said. "I think I still playing the same level before that point and after that point."
After dominating the tiebreak, Nadal raced through the second set, leaving Berdych with a familiar sinking feeling. The 25-year-old Czech has now lost 19 straight sets to Nadal, including this year's Wimbledon final.
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Serving for the win at 5-1, Nadal even had the confidence to try a through-the-legs winner, and although that dropped millimeters wide, he still finished with 27 winners to Berdych's 18.
Roddick, who had qualified for the eight-man tournament for the eighth straight year, leaves London with an 0-3 record after a surprisingly lackluster performance on Friday.
The 28-year-old American had won his last four matches against Djokovic and engineered a break point in the opening game, only to put a backhand into the net.
Roddick failed to threaten again. A forehand into the net handed Djokovic his first break of the set at 2-1, and Roddick went on to rack up 22 unforced errors as his season ended with a whimper.
"Feel I've been struggling physically on and off for a while now," Roddick said. "I am looking forward to resting for 10 days and then trying to get in shape. It probably came to an end at about the right time."