Playing on his least favourite surface, in his nightmare conditions and on the brink of going two-sets-to-one down, Roger Federer concluded his bumpy victory in the French Open second round on Thursday had been "fun".

The Swiss world number two saved a set point at 5-2 in the third set on his way to a 7-6, 5-7, 7-6, 6-2 victory over Argentine Jose Acasuso.

"It was sort of a fun match to be part of with so many ups and downs," Federer told a news conference.

"I'm not part of such close matches that often. So when they happen, it's great to put in the fight when you can. Definitely it was a sign of mental strength and the physical abilities I have."

A fan of hot weather that speeds up the clay, the Swiss did not relish the cool and damp conditions on Philippe Chatrier court which played into the hands of claycourt specialist Acasuso who has won three titles on the surface.

"I think conditions made it definitely hard today for the players. It was slow, so you had to really be very patient and that might have played in his favour," said Federer.

"Conditions were very slow, extremely slow. It was even raining in the beginning. So of course that takes away game plans because you can't just attack the net blindly and try to bluff your way through a match like this."

The Swiss seemed uncomfortable in a protracted first set, with the 13-times grand slam winner having to save five break points in the fourth game after Acasuso dealt deftly with two Federer smashes that would normally have been winners.

The pair traded breaks in the sixth and seventh games before it eventually went to a tiebreak where Federer saved four set points before pulling back to snatch the set for himself with a tidy dropshot.

Acasuso, who knocked out second seed Andy Roddick at Roland Garros in 2005, gave the Swiss a few lessons in how to play on his least favourite surface in the second.

Sliding around with ease, the 26-year-old Argentine hit some excellent passing shots while Federer's unforced errors continued to mount.

The second seed was 5-1 down in the third set before winning five games in a row to force a tiebreak which he bagged with a sizzling serve that his 45th-ranked opponent could not control.

After seeing his chance of a big upset evaporate in the third set, Acasuso went out with a whimper in the fourth when he messed up a service return.

"I'm angry. Because even though it was Federer, it was a near miss," the 26-year-old Argentine said.

"I was so close to winning this match but what's positive is that I played really well. I could have won three sets but then he played really well."

Federer meets France's Paul-Henri Mathieu in the next round.