Rafael Nadal reached the third round of the Cincinnati Masters on Wednesday only to immediately write off his chances of winning the title.
In just his second event back after two months out with tendonitis in both knees, the Spaniard's rehabilitation continued with a 7-6 7-6 victory over Andreas Seppi of Italy.
The 23-year-old, who has dropped to third in the rankings, showed signs of returning to his best form but had to save nine out of 10 break points to see off the Italian.
Frenchman Paul-Henri Mathieu is his next opponent and Nadal said that going all the way this week would be almost impossible.
"Here the ball is fast and the ball is not getting big top-spin, so it's tough," he said.
"It's difficult conditions for me. My results here in this tournament say that. My best result was last year, semi-finals. It's always difficult for me to play a good tournament here."
Nevertheless, Nadal said he was happy with the way he battled past world number 45 Seppi.
"I don't know if I played very well but I was there all the time," he said. "I was fighting for every point, and that's the important thing.
"I don't know if it was a very good match for me, but it was very important, because these matches helped me a lot to get my best performance and to get physical training, too.
"So everything is positive. And the most positive thing is that tomorrow I am going to be another time on the court.
"Probably I am not playing, that's true, my best tennis. But even if I play my best tennis, the match is never going to be easy against Seppi."
Roddick upset
Meanwhile, American Andy Roddick's U.S. Open preparations suffered a blow on Wednesday when he was upset 7-6, 7-6 by countryman Sam Querrey in the second round.
The world number five, runner-up at Wimbledon last month, had set points in the first set and was a break up in the second but could not push home the advantage.
"That first set was huge for me," Querrey said in a courtside interview. "I lost a tiebreak against him in Washington a few weeks ago and then lost the second 6-4, so that was key tonight."
World number 26 Querrey, who clinched his second ATP title at the LA Open earlier this month, will play Australian Lleyton Hewitt in the third round.