World Tour Finals: Tomas Berdych beats Marin Cilic in London

Tomas Berdych reignited his ATP World Tour Finals challenge with victory over out-of-sorts US Open champion Marin Cilic in London.

Czech Berdych won their crucial Group A contest 6-3 6-1, after both men lost their opening matches on Monday.

Novak Djokovic and Stan Wawrinka meet in Wednesday's late match, with a first semi-final place up for grabs.

Berdych will play Djokovic and Croat Cilic faces Wawrinka in Friday's final round-robin matches.

Two heavy defeats mean Cilic is all but out of the tournament, leaving Berdych to try and take one of the semi-final places from Wawrinka or Djokovic.

"I was really trying to focus on my tennis and my game, trying to go point by point," said Berdych.

"Today was more fighting and getting through. It's good to have a win and it always counts.

Berdych is making his fifth consecutive ATP Finals appearance

"It's not my first year. I have the experience of losing the first match in the past and I know how to come back. That was the biggest difference today."

The crowd was noticeably down on previous matches as the two group outsiders returned to the scene of Monday's humiliation, when between them Berdych and Cilic won just four games and managed one hour and 54 minutes of action.

If nothing else, they at least managed to stay on court for one hour and 14 minutes second time around.

Berdych also extended his remarkable record of having lost all five of his opening matches at ATP Finals, yet won all five of his second matches.

The pair continued in the same vein as Monday in an error-strewn opening game that lasted seven minutes and ended with Cilic netting a forehand when facing a fourth break point.

He looked a shadow of the player who won his first Grand Slam title in New York two months ago, and coach Goran Ivanisevic could hardly bear to watch from the sidelines.

Cilic briefly strung together some quality with a smash and a volley on his way to earning two break points in game eight, but he could not convert, and another loose forehand gave up the set moments later.

Winners were few and far between but Berdych was making half the number of unforced errors, and he fired down an ace to see off break point early in the second.

Cilic's failure to trouble the Berdych second serve was just one of several factors letting him down and, after he found the net with a backhand to fall 3-1 behind, his challenge quickly faded.

"Of course it's a little bit of a disappointment to lose the matches like I did, but I played against the guys who are at the top of the game," said Cilic.

"Considering everything, I didn't play well, and the outcome is not going to be much different.

"But having won a US Open is going to make this season look amazing, so that's always a huge, positive part to looking into the things."

Big-serving Marin Cilic won just 41% of points on his second serve - compared to 70% for Berdych

Berdych must now beat world number one Djokovic to try and qualify for the last four - and he asked the O2 crowd for any tips

Marin Cilic's ATP finals debut is now as good as over with two heavy defeats - he must thrash Wawrinka and hope other results go his way