Washington, Aug 5 (DPA) Argentine Juan Del Potro rescued his title defence at the Legg Mason Classic tennis tournament with a post-midnight finish, holding off Yen-Hsun Lu 4-6, 6-3, 6-2 in the second round.

The world number six South American, making his return to the game after Wimbledon and the Davis Cup last month, Tuesday had to labour to get past the Taiwan challenger ranked 62.

A year ago, Del Potro produced the tennis of his life while still a month shy of his 20th birthday, winning the fourth of his five ATP titles while playing the event.

He also won Los Angeles, Kitzbuehel and Stuttgart and started 2009 with a trophy at Auckland, his last major success.

Croatian Marin Cilic, the number six seed, was the first elite casualty of the week as he lost to Indian qualifier Somdev Devvarman 7-5, 6-4.

The Asian had been down a set in his final qualifying match at the weekend and has carried his momentum forward into the main draw.

The 24-year-old won back-to-back national university tennis titles in 2007 and 2008 when studying at University of Virginia.