Mason: 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.
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, dropping just six points on serve and hitting nine aces.
Tsonga had suffered an arm injury that caused him to withdraw during his semi-final against Serbia`s Novak Djokovic at the Montreal Masters last week but he looked to be striking the ball without any hindrance on Tuesday.
"I didn`t play the last two days because of my arm, and this morning at the warmup I was feeling really good. It was a really fluid match. Everything was easy for me today, including my serve," Tsonga said.
Berdych, the eighth seed, breezed through his second round match against Argentine Juan Monaco in straight sets 7-6, 6-0, winning 83 percent of first serve points.
Compatriot Stepanek, who had to qualify, came out on top against big-serving American John Isner 7-5, 5-7, 7-6 in a tough first-round encounter lasting two hours and 46 minutes.
Stepanek triumphed, despite 21 aces from Isner, and the Czech saved three break points in the final set.