MUNICH - Juan Martin del Potro made a successful clay-court comeback after three years away when he beat Dustin Brown 7-6 (2), 6-4 to advance to the second round of the BMW Open on Wednesday.

Del Potro won the U.S. Open in 2009 and was ranked as high as No. 4 in the world until a long-lasting wrist injury hindered his career.

A wild-card entry into the Munich tournament, del Potro cruised in the tiebreaker and went up two breaks in the second set. But the Argentine could not serve out the match at 5-1. Brown saved a match point with a backhand winner down the line to cut the deficit to 5-4.

But the erratic Brown could not hold serve while trying to even the set. The German saved two more match points before committing a double-fault on the third.

Also, third-seeded Dominic Thiem of Austria became the first player to reach the quarterfinals when he beat Santiago Giraldo of Colombia 7-5, 6-4. Ivan Dodig of Croatia beat sixth-seeded Thomaz Bellucci of Brazil 7-6 (5), 6-3 in another second-round match.

Earlier, second-seeded Gael Monfils pulled out of the event with a groin injury sustained in practice. Monfils said cold weather may have been behind the injury or "because I've played a lot recently."

It was the third consecutive year that Monfils had to withdraw from the clay-court event because of injury. The Frenchman had a bye into the second round.

The weather has been unseasonably cold this week in Munich, with rain and even snow disrupting the schedule.

Del Potro and others played in long sleeves and leggings as the temperature remained cool.

In first-round action, fifth-seeded Fabio Fognini advanced by beating Maximilian Marterer 6-3, 6-1, eighth-seeded Alexander Zverev outlasted Malek Jaziri 4-6, 6-3, 6-2, and Jan-Lennard Struff eliminated seventh-seeded Vasek Pospisil 6-7 (5), 6-3, 6-2