Mahesh Bhupathi with partner Mark Knowles during their doubles round robin match at the O2 Arena in London on Tuesday. (AFP)

London: Juan Martin del Potro held on to beat Fernando Verdasco 6-4, 3-6, 7-6 (1) Tuesday in his second round-robin match of the ATP World Tour Finals here at the O2 Arena.

Mahesh Bhupathi and Mark Knowles enhanced their semi-final chances at the ATP doubles event after edging past Mariusz Fyrstenberg and Marcin Matkowski in a tough group B encounter here also on Tuesday.

The third seed Indo-Bahamian pair overcame a first set lapse to beat the eighth seeded Polish pair 3-6, 6-3, 10-7 in a battle that lasted one hour and 15 minutes. Bhupathi and Knowles had defeated fifth seeds Frantisek Cermak and Michal Mertinak in their first match on Sunday and with second win in a row they are on top of the Group B.

“The easiest way to control your destiny is to win all three matches. That’s been our goal. We’ve gotten two down and we’ve got one more to go. The positive is we have two wins now and the pressure is on the other teams,” Bhupathi said.

Bhupathi’s Bahamian partner was all smiles after the win. “We’re excited, very excited. Especially because they were playing extremely well,” Knowles said.

The fifth-ranked Argentine rebounded from his opening loss to Andy Murray at the season-ending tournament, trading powerful forehands and accurate backhands with Verdasco throughout the match.

But Del Potro did waste two match points in the third set before winning in the tiebreaker.

Del Potro will likely have to beat Roger Federer on Thursday in his final match of the round-robin phase to advance to the semi-finals. Verdasco, with two losses, will face Murray.

Del Potro and Verdasco traded powerful forehands and accurate backhands throughout the match, but the US Open champion had the advantage through much of the third set and earned his second break of the match in the sixth game — and he did it with the help of instant replay.

Verdasco sent a shot toward the baseline, and Del Potro played it cleanly and sent it back over the net. But he also immediately raised his arm to challenge the call, believing it was long. He was right, and the reversal gave him a 4-2 lead.

After holding serve in the next match, Del Potro earned his first match point with Verdasco serving, but the Spaniard saved that with a backhand winner. Then serving for the match at 5-3, Del Potro sent a pair of shots long to give Verdasco his second break of the match.

In the next game, however, Del Potro earned another match point but sent a backhand into the net. The tiebreaker was all Del Potro, while Verdasco missed five straight forehands on the final five points.

Del Potro dominated on his serve for most of the first set, losing only three points before giving Verdasco a pair of break points in the final game. Both, however, were saved.

In the second set, both players held serve relatively easily through 3-3. Verdasco then made it 4-3 despite trailing 0-30, and soon broke for 5-3 after Del Potro sent a pair of backhands long.

Meanwhile in Monday’s late matches, Nikolay Davydenko was beaten by Serbia’s defending champion Novak Djokovic 6-3, 4-6, 5-7 in a repeat of last year’s final when the season-ending climax was staged in Shanghai.

Djokovic, the form player arriving at London’s spectacular O2 Arena after three titles in his last four tournaments, finally subdued the jet-heeled Russian after nearly three hours of high-quality action before swapping shirts, soccer style, at the net.

Also, Leander Paes and his Czech partner Lukas Dlouhy began their campaign with a loss. They were handed a straight-set defeat by debutants Lukasz Kubot and Oliver Marach in their opening Group B match here.

The fourth-seeded Indo-Czech pair went down 3-6, 6-7(3) to the sixth seeded Polish-Austrian rivals in their opening match and will now be up against second seeds Bob and Mike Bryan of Unites States, who also started their campaign on a disappointing note, losing 4-6, 4-6 to seventh seeds Max Mirnyi and Andy Ram.