Djokovic reaches Masters Cup semis

SHANGHAI (Reuters) - Australian Open champion Novak Djokovic survived a second-set implosion to beat Russian Nikolay Davydenko 7-6 0-6 7-5 on Tuesday and become the first player into the semi-finals of the Masters Cup.

The world number three lost all three of his matches without winning a set on his Masters Cup debut last season but is now guaranteed to top the Gold Group.

"It's a great achievement for me, going through to the semi-finals," said the 21-year-old Serbian, who won his opener against Juan Martin Del Potro on Sunday.

"Last year wasn't that much fun for me. It's different this year because I'm coming here as a grand slam winner and more mature player, stronger mentally and physically on the court."

Argentine Del Potro beat Jo-Wilfried Tsonga 7-6 7-6 in the other group match to keep alive his hopes of reaching the knockout stage and end those of the Frenchman.

Davydenko, who beat Tsonga in his Sunday opener, will now take on Del Potro in a winner-takes-all match on Thursday with a place in the semi-finals of the $4.45 million season finale on the line.

The 27-year-old Russian was at his dogged best at the start of Tuesday's match, darting around the court to break the second-seed on his first service game.

Djokovic was playing well, though, and he broke back when the fourth seed was serving for the set before winning the tiebreak courtesy of a couple of thundering aces and a double fault.

The young Serbian fell apart in the second set, smashing his racket about and seething when a line call and subsequent challenge went against him.

"I was quite nervous and a bit shaky," Djokovic explained. "I just wasn't myself in that second set and I lost that desire and played very bad."

Davydenko, a seasoned campaigner playing in his fourth Masters Cup, seized his chance to even up the match in 26 minutes and grabbed two break points on Djokovic's first service in the decider.

"I don't know what happened in the second set," said Davydenko. "I was surprised but I knew he would come back."

Djokovic did regain his composure and saved his serve. The match looked destined for another tiebreak when he broke for 6-5 and served out for victory.

Seventh seed Del Potro made a great start to his second Masters Cup match by breaking Tsonga's first service game and always looked the more likely to win a tight contest.

"I know his game," said the lanky 20-year-old. "I know what can I do against this player, and that's what I did today. I played very good."

Tsonga served up 17 aces and rattled home 42 winners but the good work was undone by 38 unforced errors, the last of which came when he put the ball in the net to end the second tiebreak.

"I lost with two tiebreaks," said the 23-year-old sixth seed, runner-up to Djokovic at this year's Australian Open. "I know he played better than me in the tiebreak. I missed some easy balls and that's it."

(Editing by Karolos Grohmann)