World number one Roger Federer hopes to turn around his bad fortune of the season at the Beijing Olympics after his another shock loss to Croat Ivo Karlovic at the Cincinnati Masters on Thursday.

Karlovic powered 22 aces and some more service winners to overcame the Swiss 7-6 (8), 4-6 and 6-7 (7), who prevailed in all their six previous meetings.

"This year was hard, I guess, with the start of the year. But nevertheless, I still think it's been a good year. I just hope I can show it now at the Olympics and the U.S. Open," said Federer, who will be playing his third Olympics.

"I'm looking forward for the next two tournaments. Those are really the ones that can make this season from a good one to a great one," he added.

Elsewhere, Rafael Nadal stayed on course for the power shift by beating German Tommy Haas 6-4, 7-6 (0) later Thursday, reaching the quarterfinals with his 31st consecutive win.

Should Nadal win the Cincinnati Masters this weekend, he would dethrone Federer, who has held top spot in the world rankings for 235 consecutive weeks (since February 2004). Federer and the Spaniard have held the top two spots since July 25, 2005.

In the opening-set tiebreak it all went with serve till 6-6 when Federer topspun a drive which was called in, only for it to be changed after Karlovic appealed to the Hawkeye. Karlovic then hit a winning forehand drive on the next point.

Federer chiselled out one break of serve in the fifth game of the second set but in the deciding third-set tiebreak, Federer suffered a chronic piece of ill-fortune.

Swiss delegation fielded Federer and Stanislas Wawrinka, who now ranked 10th in the world, to the Beijing Olympic tennis event.

(Xinhua News Agency August 1, 2008)