Fourth seed Stan Wawrinka was in a happy mood after overcoming David Ferrer in their group-stage clash at the ATP World Tour Finals on Wednesday.
Swiss star Wawrinka showed fighting spirit as he rallied to beat Ferrer 7-5 6-2 in London.
Spaniard Ferrer led 3-1 and served for the opening set at 5-3 before a double fault offered Wawrinka an avenue back into the match.
The French Open champion made the most of his opportunity, breaking back to level the contest at 5-5 before serving out the set, and he did not look back in the second as he tallied his 54th win of the season.
"My game started to feel better out there," said Wawrinka.
"I didn't start well. I started to play a little bit better the middle of the first set. I'm a little bit lucky he gave me back the game to come back.
"I'm quite happy with the win, especially to turn around the first set and finish that way."
Wawrinka - beaten by Rafael Nadal in his first match - will now face Andy Murray for a place in the semi-finals.
"Andy is an amazing player. He's number two this year, he's had an amazing year," the 30-year-old added.
"He's always tough to play, especially at home. I'll look forward to that match."
Ferrer, meanwhile, has now opened the tournament with back-to-back defeats.
The 33-year-old lost all three round-robin matches in 2013.
"I tried to do my best. The key was in the first set. I was up 5-3 to win the set and I did mistakes, important mistakes. I lost that game and maybe my focus," Ferrer said.
"In the second, Wawrinka was playing better. He deserved to win. He was better than me."