In a quarter-final clash between two Barclays ATP World Tour Finals contenders Friday, fifth seed Radek Stepanek battled to defeat fourth seed Marin Cilic 4-6, 6-3, 6-3 at the Davidoff Swiss Indoors Basel, an ATP World Tour 500 tennis tournament.

At 870 points behind eighth-placed Fernando Verdasco, No. 13 Cilic still has a slim chance of qualifying for the season finale, but will fall out of contention if the Spaniard reaches the final in Valencia this week. Stepanek, currently 12th in the year-to-date South African Airways 2009 ATP Rankings, today added 90 points to his total by reaching the semi-finals and is 430 points behind No. 11 Jo-Wilfried Tsonga.

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The 30-year-old Stepanek recovered from the loss of the opening set in his third meeting with Cilic to hit back and break serve once in the second set and twice in the decider to clinch victory after two hours and two minutes, improving to a 2-1 career lead over the Croatian.

The Czech has reached three ATP World Tour finals this season, capturing his third and fourth titles at the Brisbane International (d. Verdasco) and the SAP Open (d. Fish) in San Jose and finishing runner-up at the Regions Morgan Keegan Championships (l. to Roddick) in Memphis. He has compiled a 44-18 mark on the year.

Stepanek next will look to improve on a 1-4 record against World No. 3 Novak Djokovic, who recorded his sixth successive victory over Swiss Stanislas Wawrinka 3-6, 7-6(5), 6-2. The Serbian withstood 13 aces from the racquet of sixth seed Wawrinka and, after levelling the match in a second-set tie-break, raced to a double-break lead in the third set before sealing victory after two hours and 18 minutes.

"Most of the match he was controlling the game," confessed Djokovic. "I didn’t feel quite fresh at the start and for a set and a half I was moving quite badly. He played really well and one of the key elements in his game, which was working well, was his serve. I had a lot of difficulty getting a lot of returns back. But I managed to hold my nerve in important moments. His level dropped in the third set, he didn’t move well, wasn’t aggressive enough, made a lot of unforced errors. So I just kept the momentum going."

Djokovic and Stepanek clashed most recently in the fourth round at the US Open, where Djokovic progressed for the loss of just seven games. Stepanek recorded his lone victory over the Serbian at the ABM AMRO World Tennis Tournament in 2006.

"I had a great match against him at the US Open, but it’s totally different conditions now," said Djokovic, looking ahead. "We’ve had a lot of matches, we know each other’s games quite well. Radek is a player who plays with a lot of talent, a lot of feel. He’s had a couple of great wins this tournament so it’s going to be a tough one.”

The 22-year-old Djokovic, who posted the first double-bagel win of his career against Jan Hernych Thursday, leads the ATP World Tour with 69 match wins (69-18 mark) this season and has captured three titles from eight finals. The Belgrade native will defend his title (d. Davydenko) at the Barclays ATP World Tour Finals in London later this month.

Three-time defending champion Roger Federer won his 18th straight match in his hometown by easing past Russian qualifier Evgeny Korolev 6-3, 6-2 in just 55 minutes. The top seed saved both break points he faced, while capitalising on three of the four chances he created to improve to a 2-0 career lead over the No. 58-ranked Korolev.

"It is very special (on the main court in Basel)," said Federer. "I used to be a ball boy here and I have so many great memories from this place. It’s really been an amazing tournament for me and obviously I love coming back here. I’ve been on this great run now with so many wins in a row; it’s very nice for me.

"I think so far the tournament’s been going really great for me. I thought the match today against Korolev was one of my best ones. He played really aggressively, there was a lot of risk involved. So, it was important that I served well and stay aggressive myself and I was able to do that today. So, I’m very pleased."

The 28-year-old Federer is bidding for his fifth tour-level title of the year, following victories at the Mutua Madrilena Madrid Open (d. Nadal), Roland Garros (d. Soderling), Wimbledon (d. Roddick) and the Western & Southern Financial Group Masters (d. Djokovic). The right-hander, who is returning from a six-week break, has won 37 of his past 39 matches, including a runner-up finish to Juan Martin del Potro at the US Open.

For a place in his sixth final in Basel, Federer will face countryman and World No. 73 Marco Chiudinelli, who continued to build on his recent success by reaching his first ATP World Tour semi-final at the expense of Richard Gasquet, defeating the Frenchman 6-1, 6-3 with four service breaks in 61 minutes. The 28-year-old Chiudinell, who is playing his hometown event for the fifth time, recently advanced to the first quarter-final of his career at the PTT Thailand Open (l. to Tsonga) in Bangkok and last week reached a career-high No. 71 in the South African Airways 2009 ATP Rankings.

"I’m playing my childhood friend, Marco Chiudinelli, who’s also making a great run in the Rankings, so it’s a big moment for both of us in tomorrow’s semis," said Federer. "We used to have the same coaches, we both used to play soccer against each other, we used to hang out as friends; we still do. He’s been injured for two years almost with surgeries, shoulder and knee problems. Now he’s finally making a big break through so I’m very happy for him. I still hope I can stop his run."