Roger Federer will put an 18-match unbeaten run on the line against old school friend Marco Chiudinelli in the semi-finals of the Swiss Indoors tournament on Saturday.

Federer, winner of this tournament for the last three, dispatched Russian Evgeny Korolev 6-3 6-2 in his quarter-final while world No. 73 Chiudinelli hammered Richard Gasquet 6-1 6-3 to reach his first semi-final.

"It's so rare that I play a good friend like this," Federer said of his school friend and former rival on the football pitch.

"It should be a great experience. Marco has really been improving this year. It will be tough but enjoyable."

Novak Djokovic stayed atop the ATP win list with his 69th victory of a draining campaign on Friday to reach the semi-finals, then admitted he's dreaming of a December vacation.

The second-seeded Serbian defeated Switzerland's Stanislas Wawrinka, the sixth seed, 3-6 7-6 (7/5) 6-2 after trailing a set and a break.

"A proper off-season should be a month-and-a-half or so," Djokvic said of a break which will amount to a month for those elite players participating in the eight-man Wold Tour Finals in London from November 22.

"I don't know what I'll do (in December) but I know I have to rest - that is just as important as work.

"I've played the most matches this season. We have some important meetings coming up in Paris (next week's Masters) and London and we need to discuss the future of our sport," said the member of an ATP Player Council headed by Federer.

"The sponsors and tournaments don't want to see top players pulling out at the last minute due to injury (from a long season). Hopefully we can work something out."

Djokovic will now face Radek Stepanek who dimmed the qualifying hopes of Croatian Marin Cilic for a last-gasp spot in the season-ending ATP finals with a 4-6 6-3 6-3 upset.

Croatia's Cilic stands provisional 12th in the points race as he fights for one of a pair of slots remaining open in London.

But after a promising start, Cilic fell victim to the court craft which has made this 30-year-old Czech opponent such a threat.

Stepanek, playing Basel for the first time, completed his turnaround win in two hours, overcoming ten aces from Cilic and breaking on all four of his opportunities.

Cilic played the final last week in Vienna and was hoping for a running start this week heading into the Paris Masters from Sunday, the last event of the regular season.

Stepanek now stands 44-18 for a year in which he earned the third and fourth ATP titles of his career in Brisbane and San Jose.

Cilic, 21, is still riding the best season of his young career, 46-20 with two titles.