Roger Federer saved four match points before beating Stan Wawrinka 4-6 7-5 7-6 in the semi-finals of the ATP World Tour Finals at the 02 in London.

Wawrinka came into the semi-final with a miserable record against his 33-year-old Swiss compatriot, having won just two of their previous 16 meetings, but had his chances to reach his first Tour Finals final.

Federer trailed 4-2 in the deciding set and missed two chances to break back in the seventh game.

Serving for victory at 5-4, the third seed had three match points but decided to serve and volley on each one and each time he came up short.

Federer levelled for 5-5 but Wawrinka missed another two break points in the 11th game and the match - the longest of the week - went into a deciding tie-break.

Federer led 4-2 with a mini-break but Wawrinka hit back to earn another match point at 6-5.

But he sent a return long and then when Federer set up his first match point a point later, the 17-time Grand Slam champion claimed victory with a stop volley.

Ninth final

That took Federer through to a ninth final in this event against world No 1 Novak Djokovic on Sunday evening.

Federer will be bidding for a seventh Tour Finals title but will have his work cut out against a well-rested Djokovic, who surrendered just three games in beating Wawrinka on Wednesday.

As for the Swiss No 2, he will have to regroup and join forces with his friend and conqueror when Switzerland take on France in the Davis Cup final next week.

Federer has met Djokovic on 36 occasions, winning 19 times, but the Serb has won their last three finals, including at the Tour Finals in 2012.

"I think I got lucky tonight. Stan played better from the baseline and that usually does the job on this court. But I kept fighting," Federer said.                  

"It's tough but I'm thrilled to be in another final in London. Novak is playing great tennis. It usually brings the best out of me, it's going to be tough but I'll give it a shot."
(Sky Sports)