Defending champion Rafa Nadal got back down to business at Roland Garros today, moving belatedly into the third round after his challenge for a record eighth title had been bogged down by dismal weather.

Idle since Monday when he struggled past Germany's Daniel Brands, the 26-year-old Spaniard was again far from his scintillating best as he dropped the first set, this time to Slovakia's Martin Klizan, before winning 4-6 6-3 6-3 6-3.

Nadal's clash with Klizan was one of several second-round matches from the top half of the men's draw which is lagging behind the bottom half occupied by second seed Roger Federer who remained untroubled with an easy win against Julien Benneteau.

Federer needed only 90 minutes to win 6-3 6-4 7-5 having taken the match by the scruff of the neck with a burst of 14 straight points towards the end of the opening set.

Nadal, bidding to become the first man to win a single grand slam eight times, started badly and was broken in the seventh game by fellow left-hander Klizan who for a while looked as though he might be able to finish the tattoo on his right calf.

"It's not finished because I am waiting for some big moments in my life," the 23-year-old Slovak said.

After dropping the first set, Nadal responded to win the next three although it was never comfortable and he has yet to catch fire.

Nadal has no tattoos but plays with the numeral "7" stencilled on to his shoes. The man from Mallorca looks like he desperately needs some Mediterraean-style sunshine if he is to have "8" decorating next year's sneakers.

It was a good day for seeded men with Tommy Haas (12), John Isner (19), Jerzy Janowicz (21) and Mikhail Youzhny (29) all winning their delayed second-round matches.

Germany's Haas, still a class act at 35, put a hole in the American challenge when he picked apart 20-year-old qualifier Jack Sock in straight sets.

Isner won an all-American clash with Ryan Harrison, coming back from two sets down to win 8-6 in the fifth - a year to the day after losing in five sets to local favourite Paul-Henri Mathieu in a 76-game epic.