The second-ranked Spaniard lost on clay for only the second time in 105 matches, falling to former No 1 Juan Carlos Ferrero 5-7, 1-6 in the second round of the Rome Masters.

Moreover, Nadal has a large blister on the sole of his right foot - and only days left to recover for next week's Hamburg Masters.

'The calendar is impossible,' he said. 'Last week, when everyone was asking me how I feel about the calendar, I said it was going to be impossible for me to play three weeks in a row. Finally they see now.'

He called for a trainer late in the second set to treat the blister, which began bothering him on Sunday when he won the Barcelona Open. The week before, Nadal won the Monte Carlo Masters.

But, on waking up in his hotel room on Monday morning, he was in such discomfort that he could not even put his foot on the floor.

'I had no power in my legs,' said Nadal, who had a first-round bye.

Ferrero said he, too, was not fully fit after his first win over Nadal in five tries.

'I pulled out of Barcelona last week with a groin problem and I felt it again yesterday against Nicolas Kiefer,' Ferrero said.

Nadal's last loss on clay came against top-ranked Roger Federer in the Hamburg Masters last May.

He had never lost at the Foro Italico, winning the Rome tournament each of the previous three years.

The 23rd-ranked Ferrero took the Rome title in 2001, two years before he was the French Open champion.

He reached the top of the rankings in 2003, on the strength of his title at Roland Garros and runner-up finish at the US Open.

Hampered in part by a series of injuries, he has struggled in recent seasons, finishing outside the top 15 every year since 2003.

'It was a very important win for me,' Ferrero said. 'I feel special right now, I haven't had this special feeling for a long time.'

The Rome Masters is an important clay-court warm-up tournament for Roland Garros, which begins on May 25.

Nadal is the three-time defending champion.

'I don't think it's going to change a lot. It's one week that he lost, and he will try again to play his level in Hamburg,' Ferrero said.

'He has a lot of time to prepare for Roland Garros.'

Four other seeded players were also upset in the second round.

Fifth seed David Ferrer fell to Radek Stepanek 6-4, 2-6, 1-6; Spanish clay-court specialist Nicolas Almagro beat seventh-seeded David Nalbandian 6-4, 7-5; Igor Andreev defeated No13 Juan Monaco 4-6, 6-1, 6-4; and Stanislas Wawrinka upset No14 Andy Murray 6-2, 7-6 (7-5).

Meanwhile, Nadal and seven Spanish players are boycotting national tennis federation promotions.

Their move follows reports that their Davis Cup semi-final against the US will be held at relatively high altitude that may help the Americans.

The players said they had been let down by federation president Pedro Munoz because the planned site in Madrid - 600 metres above sea-level - will favour the faster-serving American team.

The semi-final is from Sept 19-21.

ASSOCIATED PRESS