NEW YORK, Aug. 31 -- Swiss mogul Roger Federer needed a second successive five-setter to reach the US Open third round on Thursday as he toiled for a 6-1, 6-7(3), 4-6, 6-4, 6-2 win over fellow veteran Mikhail Youzhny of Russia in three hours.

It was the Australian Open and Wimbledon champion's 17th win in 17 matches against Youzhny in a rivalry stretching back to 2000.

Five-time US Open champion and third seed Federer had also needed five sets to see off US teenager Frances Tiafoe in the opening round.

"It wasn't always like this," the Swiss player said. "Back then, I used to win or lose in straight sets. But battles can be fun. I feel quite warmed up now."

"Losing that second set was huge for him, tough for me. It really put me in a tough spot there," he added. "I had to come up with something."

The 36-year-old Federer will face 35-year-old Feliciano Lopez of Spain for a place in the last 16.