"I don't feel confident. But I'm going to try and need to improve on that," admitted Nadal ahead of Queen's.
Nadal will team up with Davis Cup doubles partner Feliciano Lopez Tuesday as the Spanish duo face British partners James Auckland and Jamie Delgado.
It will mark Nadal's first appearance at the London tournament where he plays he opens his singles campaign later after a first round bye.
ATP Queen's Club
Hewitt king of Queen's
18/06/2006 AT 14:29
"I know the normal thing is I'm going to lose in Queen's first round because is very difficult to adapt in just two days," he said in Paris on Sunday.
"But this year I want to concentrate... and play good matches because that's important for building up confidence for Wimbledon."
"It's very difficult to move the same on grass because skid a lot," said the 20-year-old. "When I go after a difficult ball and then turn back, I skid.
Nadal has won one just one match on tennis's fastest surface over the past 12 months, a first round win over American Vince Spadea at Wimbledon.
In the second round he was beaten in a four-set by Luxembourg's Gilles Muller.
Nadal said positive thinking was key to his victory over Federer in Paris and he is not about to give up on grass.
But it will be tough.
At Queen's, he'll test his skills on even faster grass than Wimbledon's and he will be up against rested, seasoned grasscourters like Andy Roddick and Lleyton Hewitt.
ATP Queen's Club
Hewitt aiming to end drought against Blake
18/06/2006 AT 10:34
ATP Queen's Club
Hewitt into 4th Queen's final
17/06/2006 AT 19:34