World number three Roger Federer cast aside bad memories to defeat Argentina's Juan Martin Del Potro 6-3, 7-5 at the Cincinnati Open.
Del Potro had upset Federer in the 2009 US Open final before injuries set back his career but the Swiss looked at is comfortable best in the first set.
It was a much closer encounter in the second set which was played to serve until the Swiss broke to go 6-5 up.
Federer had missed out on six break points prior to winning that game. He then held serve to go through to face American James Blake.
"I expected a tough match with Juan Martin for obvious reasons, and it went better than I thought," said a relaxed Federer. "I thought I played a wonderful first set and a very good second set, too. That was obviously enough tonight.
"I don't think I really allowed Juan Martin to be able to play the game he usually plays.
"It's quick conditions, so you're never going to maybe find the rhythm like you would on a slower court. But I was able to mix it up well, I served well, and did all the right things tonight."
France's Jo-Wilfried Tsonga looked back to full fitness while Czechs Tomas Berdych and Radek Stepanek came through their first tests. Wimbledon semi-finalist Tsonga defeated Croat Marin Cilic 6-3, 6-4 in the opening round, hitting nine aces.
Tsonga had suffered an arm injury that caused him to withdraw during his semi-final against Serbia's Novak Djokovic last week.