* Djokovic beats Cilic
* Del Potro downs Chardy
* Swiss men through (Updates after Federer, Wawrinka wins)
By Simon Evans
MASON, Ohio, Aug 17 (Reuters) - World number two Novak Djokovic has a shot at revenge against Juan Martin del Potro, who ended the Serb's medal hopes at the London Olympics, when the two clash in the Cincinnati Open semi-finals on Saturday.
World number one Roger Federer, who dealt with American Mardy Fish 6-3 7-6 in some style, will play his Swiss Davis Cup team mate Stanislas Wawrinka in the other semi.
Djokovic, who lost to former U.S. Open winner Del Potro in the Olympic bronze medal match less than two weeks ago, enjoyed a routine 6-3 6-2 victory over 12th seeded Croatian Marin Cilic on Friday to advance.
"It was my best match so far here in this tournament and came in the right moment, really," Djokovic, who had an easy passage through to the last eight after Russian Nikolay Davydenko retired injured during their match, told reporters.
"I had the biggest challenge today with Cilic who has been playing well the last couple of months and I played a really good match."
The five-times grand slam winner may have added incentive on Saturday given Serbia's Davis Cup semi-final loss to Argentina last year in which Djokovic retired against Del Potro.
"All these losses made me stronger and, yes, they are difficult, especially when you're playing for a country and when you're in Olympic Games and we're fighting for bronze medal," said Djokovic.
"He won that match. It happens. It's a sport. You lose, you win, but the most important thing is to try to move on and become even better and even stronger from those experiences and try to win."
Del Potro overcame the surprise player of the tournament, Frenchman Jeremy Chardy, who entered the draw as a lucky loser and reached the quarter-finals thanks to wins over American Andy Roddick and Olympic champion Andy Murray.
The tall Argentine needed just 76 minutes to make sure Chardy's run stopped, surrendering only 12 points on serve and breaking Chardy four times in a 6-1 6-3 rout.
Four-times Cincinnati winner Federer broke in the first and final game of the first set, looking in good shape against Fish, a hard court specialist who finished runner-up to the Swiss in the 2010 final.
Fish stuck at his task in the second set but the world number one turned it up a notch in the tie-break which he won to four.
"I'm very pleased that I was able to play at a high level and keep there throughout the match," said Federer, who now comes up against compatriot and friend Wawrinka.
Wawrinka, ranked 26th in the world, beat big-serving Canadian Milos Raonic 2-6, 7-6, 6-4.
After making the most of his only break point opportunity early in the third set, Wawrinka then saved two at 4-3 before wrapping things up in his next service game.
"I'm playing great tennis after two tough months. I lost in the first round at Wimbledon, Gastaad and the Olympics and it wasn't easy, but I am glad to be back on the hard court," he said. (Editing by Frank Pingue/Patrick Johnston)