Doha, Qatar (SportsNetwork.com) - Towering Croat Ivo Karlovic stunned world No. 1 star Novak Djokovic amid a sandstorm in Thursday's quarterfinal action at the season-opening $1.22 million Qatar Open.

The 6-foot-10 Karlovic, the tallest player in the history of the ATP World Tour, ousted the Wimbledon champion Djokovic in 6-7 (2-7), 7-6 (8-6), 6-4 fashion in 2 hours, 15 minutes on the hardcourts at Khalifa International Tennis Complex.

"Dr. Ivo" swatted 21 aces, including four straight to close out the final game of the match. The Croat recorded the only break of serve in the bout in the seventh game of the final set.

"It was unbelievable," Karlovic said during his on-court interview following the match. "When I arrived here, I didn't expect that one. He wasn't able to show his full range because it was windy. I just focused on my game and in the end I was a little luckier."

Karlovic is now 2-1 lifetime against Djokovic, including a perfect 2-0 on hardcourts. He also claimed his second career victory over a world No. 1, with his previous win over a top-ranked player coming at the expense of Roger Federer in Cincinnati in 2008.

Also on Thursday, third-seeded Czech slugger Tomas Berdych drilled sixth- seeded Frenchman Richard Gasquet 6-2, 6-1, fourth-seeded Spanish veteran David Ferrer whipped German Dustin Brown 6-2, 6-2 and Italian Andreas Seppi dismissed Croat Ivan Dodig 7-5, 6-4.

Friday's semifinals will pit Berdych against Seppi and Ferrer versus Karlovic.

Doha serves as a tune-up for the Australian Open.