CINCINNATTI: Americans Mardy Fish and Andy Roddick posted quarter-final victories at the three million dollar Cincinnati Masters tournament on Friday.

Former world number one Roddick defeated Serb second seed Novak Djokovic 6-4, 7-5 in a 83 minute match.

"Novak probably didn`t play his best today," Roddick said. "I was missing a lot in the first set, but my second serve got me through.

"Then the second set I was able to kind of land a couple more fist serves."

Roddick hammered eight aces against Djokovic who appeared in the last two Cincinnati finals, losing to Roger Federer last year and Andy Murray in 2008.

In another quarter-final match, Federer beat Russian Nikolay Davydenko in straight sets 6-4, 7-5.

Former US Open winner Roddick will face Fish in Saturday`s semi-finals. Fish won their most-recent match last month in Atlanta.

"He`s probably my best friend on tour," Roddick said of Fish. "So I`m really happy to see him playing well. I just hope he doesn`t do it tomorrow."

Unseeded Fish toppled world number four Murray of Scotland 6-7 (7/9), 6-1, 7-6 (7/5).

Fish sealed the victory and became the first unseeded player since Lleyton Hewitt in 2007 to reach Cincinnati`s final four when Murray dumped a forehand into the net to end a gruelling encounter in torrid temperatures.

Murray, who triumphed last week in Toronto, received massages on both legs during several changeovers, but was able to take a 4-2 lead in the second tie-breaker.

Fish then reeled off four straight points, the last when Murray went wide with a forehand passing attempt.

The miss had Murray belting a ball out of the court in frustration.

BDST: 1314HRS, August 21, 2010