The world number one had never previously dropped a set in six matches against the 12th-seeded Spaniard, but this time he slipped to within an inch of going break point down in the seventh game of the final set, before surviving 6-3, 4-6, 6-3.

This struggle followed an even tighter three-set battle in Federer's opening match on Wednesday against Juan Monaco, an Argentine ranked outside the top 50, and his loss to an opponent outside the top 50, Filippo Volandri, in the Rome Masters last week.

That setback made it the first time Federer had failed to win a title in four successive tournaments since he became world number one 171 weeks ago.

For a set and a half Federer timed the ball better than at any time since reaching the final in Monte Carlo last month, and he looked well on top of Ferrer until he reached a lead of 4-2 and 30-15 in the second set.

At that stage Federer made one mistake with a forehand and then attempted two ambitious strokes - straightening a diagonal by striking a forehand drive down the line, and launching a spectacular forehand drive volley - and saw both go wide.

He had employed what was arguably the right policy - with a perceived need to dominate opponents a little more, especially Rafael Nadal, on the Parisian clay at the French Open starting later this month - but these three mistakes not only cost him his service game, they allowed Ferrer back into the match.

Suddenly the hard-running Spaniard began to play more confidently, adding new dimensions to a game which was often based around making forehand drives from almost every position on the court.

Ferrer broke Federer again, courtesy of a net approach and a nicely angled volley, served out comfortably for the second set, and held on hard throughout the first six games of the third set.

It was then that Federer had an important piece of luck. At 3-3, 30-30 on Federer's serve a Ferrer short slice stayed very low, and Federer only managed to get it over the net via the net cord, whence the ball dropped dead.

Ferrer hopped and tossed his racket in frustration, and he never got as close to troubling Federer again, despite fighting bravely to save four break points in the next game.

Federer broke at the fifth attempt with a brilliantly angled short backhand cross court which opened up acres of court for an inevitable forehand winner, and then served out for the match without fuss.

The world number one had certainly had his moments despite the disappointing failure to close out the second set, and he can take comfort from the match practice investment of employing a full range of attacking options - and still surviving.