Tomas Berdych of the Czech Republic celebrates winning his tennis match against Marin Cilic of Croatia at the ATP World Tour finals at the O2 Arena in London November 12, 2014. [Photo/Agencies]

Berdych, who lost his opening match to Wawrinka, recovered to stay in contention for a spot in the semifinals by beating Cilic 6-3, 6-1.

Following his straight-sets loss, the Czech looked better against Cilic, hitting with accuracy and serving well on the big points.

"I think today was more fighting and getting through. It's good to have a win and it always counts," said Berdych, who is competing at the season finale for the fifth time.

Berdych has never won his opening match of the round-robin stage, and never lost his second match.

"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. I think that was the biggest difference today," he said.

Berdych broke twice in the first set as the US Open champion _ who is now 0-2 _ struggled with his serve.

Cilic, who has beaten Berdych twice this year at Wimbledon and the US Open, got off to the worst possible start as he dropped serve immediately. The hard-hitting Croatian produced some good winners but was inconsistent throughout, failing to convert any of his six break points.

In the second set, Cilic held to level at 1-1 but hardly fought as Berdych won five consecutive games to wrap up the match. Cilic, one of three debutants at the O2 Arena, was routed 6-1, 6-1 by Djokovic in his first match and has won only six games in two matches.

"Let's put it this way, with the way he played, he would never win the US Open," Berdych said.