ROME: World number one and top seed Rafael Nadal progressed to the semi-finals of the ATP Rome Masters claycourt tournament after a gruelling 6-3, 6-3 victory against sixth seed Fernando Verdasco on Friday.

The scoreline did not do justice to a keenly contested match that lasted 1hr 50min and in which Verdasco had more than enough chances to cause an upset.

The final statistics told the story of a match in which the former three-time champion here Nadal took his opportunities while Verdasco let his slip by.

Verdasco hit 20 winners to just six by Nadal but made more than twice as many unforced errors -- 41 to just 20 from the world's best player.

And both men forced six break points throughout the match but while Nadal converted four of his, Verdasco managed only one break.

Nadal said he had to adapt to conditions that had changed from his night-time victory over Swede Robin Soderling the day before.

"Last night the court was slow; the ball was heavy. Today was completely different conditions, the ball was flying so much," he said.

"I liked the conditions of today but after the change from last night, it's a big change.

"Last night I played really well and today I didn't play my best. I made some mistakes, especially in the second set.

"The beginning, I had a lot of mistakes. The first set was okay, I did well. But in the second I was a little bit lucky, he made important mistakes in some important points."

Verdasco, the 25-year-old sixth seed, started badly, double faulting to hand Nadal a break in the opening game.

However, he hit straight back as Nadal played a dreadful service game and was broken to love.

The top seed soon clicked into gear, though, and broke Verdasco twice more to take the set.

The main difference in the opener was that Nadal was massacring Verdasco's second serve, winning 78 percent of the points when his compatriot missed his first service.

In the second set Verdasco had plenty of opportunities to get his nose in front but he missed three break point chances in the first game and two more at 2-2.

Even so, he was trading wilfully with Nadal from the back of the court and but for his high unforced error count he looked capable of beating the king of clay.

But at 4-3 to Nadal, Verdasco missed two simple volleys as he gifted his compatriot a break, despite having led 40-15.

He called for the trainer at the change of ends and his knee seemed to be giving him some pain, so it was unsurprising that he wilted easily in the final game.

Nadal took his win streak on clay to 28 matches since he was beaten here a year ago in the second round by Juan Carlos Ferrero.