Juan Martin Del Potro bounced back from his opening match defeat to Andy Murray by defeating No.7 seed Fernando Verdasco 6-4, 3-6 7-6, (7-1).
The world No.5 took the first set due to his impressive serve, winning 85% of his first serve points, and breaking his opponent in the third game and sealing the set in 38 minutes.
However Verdasco, who was also looking for his first victory at the end of season event, raised his performance to claim the second set and level the match, breaking the Del Potro serve in game eight.
The third set appeared to belong to Del Potro as he raced into a 5-2 lead and with the the Argentinian at match point, Verdasco needed to respond.
The tournament debutant clawed his way back to 4-5 before saving another match point and then forced a tie-break which Del Potro won to 7-1 to take victory in 2 hours and 23 minutes.
In the doubles event this afternoon, No.3 seeds Mahesh Bhupathi and Mark Knowles moved ever closer to a place in the knockout stages of the event after winning a closely fought tie against No.8 seeds Mariusz Fyrstenberg and Marcin Matkowski, 3-6, 6-3, 10-7.
After losing the first set against the Polish pairing, it looked as if it would be the No.8 seeds who would continue their fine form after a surprise first round win over the defending champions and No.1 seeds Daniel Nestor and Nenad Zimonjic.
The Poles broke serve in the sixth game and produced a solid service display as they dropped just three points on serve to gain the early advantage.
However Bhupathi and Knowles responded in the second set, gaining a break of serve in the fourth game and playing out the set to level the match and force a deciding Match tie-break.
The pair continued to dominate in the tie-break, racing into an impressive 5-0 lead and despite a brief fightback from their opponents, Bhupathi and Knowles were able to hang on for their second victory in Group A, which leaves them in a strong position at the top of the group.
“They were playing really, really well there in the first set. We just kind of rode them out and were able to return well and turn the match around. We played really solid at the end and kind of raised our level” said Knowles.
Tonight’s doubles match sees No.1 seeds Nestor and Zimonjic attempt to bounce back from their opening day defeat as they take on Frantisek Cermak and Michal Mertinak, whilst the day’s play ends with British No.1 Andy Murray up against world No.1 Roger Federer.
For more information on who is competing in London
Follow British Tennis on Twitter @BritishTennis