Seven-time French Open champion Rafael Nadal says making the annual transition from clay to grass courts is his "biggest challenge."

The Spaniard was speaking Wednesday ahead of his first match at the Gerry Weber Open, a warm-up tournament for Wimbledon.

The "King of Clay" beat top-ranked Novak Djokovic at Roland Garos to claim his 11th Grand Slam title on Monday. He says playing on grass is "a drastic transition with the way you move and your hitting routine."

Nevertheless, he says "I will give everything possible to win this title, and that means in every single minute."

Nadal opens his singles campaign against Lukas Lacko of Slovakia on Thursday, when five-time winner Roger Federer takes on Florian Mayer of Germany in his first match.