Nov. 24 (Bloomberg) -- Fifth-seeded Juan Martin del Potro of Argentina defeated Spain’s Fernando Verdasco in three sets in the group stage of tennis’s ATP finals in London.

The 21-year-old won 6-4, 3-6, 7-6 (7-1) over the seventh- seeded Verdasco, a 26-year-old lefthander from Madrid.

The 6-foot, 6-inch Argentine made it more difficult than it had to be, allowing Verdasco to come back from 5-2 to even the match at 5-5 in the last set. The loss leaves Verdasco at the bottom of Group A without a win. Top-seeded Roger Federer and No. 4 Andy Murray, who both have one win, play later today.

“It wasn’t easy,” Del Potro said in a court-side televised interview. “I’m very happy, it’s great.”

He said he needs to play better in his next match to have a shot at making the semifinals. The Argentine failed to convert a match point when leading 5-2 in the third set. He let Verdasco back into the match, failing to convert a second match point leading 5-4, before taking his third in the tie-break as Verdasco hit a forehand wide.

Del Potro will play Federer and Verdasco faces Murray in the final Group A matches later this week.