Spain's David Ferrer extended his winning run to 11 matches with a hard-fought 6-3, 3-6, 6-4 victory over Juan Martin del Potro at the ATP Tour Finals on Tuesday.
Ferrer arrived at London's O2 Arena in the best form of his life after winning his first ATP 1000 event, the highly-regarded tournaments which are just one level down from a Grand Slam, at the Paris Masters on Sunday.
The 30-year-old's triumph in Paris came a week after he won the Valencia Open and he walked onto court against del Potro with a Tour-best 72 match wins, as well as seven ATP titles, to his name over the last year.
Ferrer had to dig deep to maintain that fine form, but he was able to do just that as he subdued former US Open champion del Potro in two hours and 16 minutes to secure a victory in his opening Group B match at the season-ending tournament.
"I am very happy. It was a top match," Ferrer said. "It was very difficult to play against Juan Martin, but I hope the people enjoyed our tennis.
"I don't know the secret of my good form. It has been the best season of my career. Maybe it's because I didn't have a big injury."
The world number five, who finished as Tour Finals runner-up in 2007, had demolished del Potro in straights sets in their last meeting at Wimbledon earlier this year, but he found it much tougher this time.
Making his first appearance in the Tour Finals since finishing as runner-up in 2009, del Potro wasted an early chance to take the initiative when he was unable to convert a break point in the third game.
And Ferrer made him pay as he landed the first break for a 3-1 lead after del Potro, cleverly manoeuvred out of position by the Spaniard, missed a backhand volley.
With the first set wrapped up with the minimum fuss, Ferrer tried to finish off del Potro early in the second, but the Argentine showed impressive grit as he saved four break points in the third game.
That was a vital show of defiance from del Potro, who then broke for a 3-1 advantage en route to winning the second set.
Del Potro shocked Roger Federer in the final of the Swiss great's hometown tournament in Basle last month and the Argentine had only lost twice indoors this year.
But Ferrer rediscovered his rhythm to break for a 2-0 lead in the decider and, although del Potro hit back with a break of his own in the seventh game, it was the Spaniard who landed the knockout blow with one more break at 5-4.
Defending champion Federer routed Janko Tipsarevic 6-3, 6-1 in the day's earlier Group B match.