World number four Novak Djokovic said he is confident to take revenge over German Tommy Haas in the quarterfinals at Wimbledon on Wednesday.

Haas beat Djokovic in the final of the Gerry Weber Open this month, denying the Serb his first grass-court title.

The 22-year-old Djokovic said he still hasn't adjusted properly to grass but he is on the right track.

"I had some good matches and some really bad matches, ups and downs in that tournament," Djokovic said.

"I was still getting used to the grass and movements, the way I should play. But here it's a different story, you know. I already played really well last two, three matches. Quite confident."

(Xinhua News Agency June 30, 2009)