Wimbeldon, England ? Roger Federer competed for all of 11 minutes Thursday. That was enough to finish off Juan Martin del Potro of Argentina, 6-2, 7-5, 6-1, for the Swiss star’s 50th consecutive victory on grass, in a match suspended overnight.

“Fifty is a great number to achieve,” Federer said. “I’m delighted about that, but I haven’t won the tournament.”

His bid to win a fifth consecutive Wimbledon title, something only Bjorn Borg has done in the past 100 years, now runs into a tougher test: a third-round showdown today against former No. 1 Marat Safin, who beat qualifier Aisam-Ul-Haq Qureshi of Pakistan, 6-4, 6-2, 7-6 (4).

The 26th-seeded Russian is only 2-7 against Federer over their careers but did beat him in the 2005 Australian Open semifinals en route to one of his two major titles.

“He’s obviously a player who can always upset anybody on any day. I hope he’s not going to have one of those crazy good days against me,” said Federer, who has a sore throat. “But I think I can pretty much control also how things are being played on grass.”