London, England -- (Sports Network) - U.S. Open champion Juan Martin del Potro pulled out a three-set victory over Spain's Fernando Verdasco in Group A play at the season-ending ATP World Tour Finals.

The Argentine star notched a 6-4, 3-6, 7-6 (7-1) victory on Tuesday in his second round-robin match of the tournament. He lost to Andy Murray in his first match on Sunday and will take on Roger Federer to close out group play on Thursday.

Verdasco lost to Federer in his first match of the tournament.

Federer and Murray are scheduled to play later Tuesday.