Big favourite Federer gives tennis betting fans a scare

US Open betting favourite Roger Federer survived a scare on Thursday when he fought off a determined fightback from Robin Soderling to reach the semi finals.

The Swiss ace has led the way in online tennis betting markets since the start of the tournament but needed to pull out all the stops in four sets on Wednesday.

He will now face Novak Djokvic in his 22nd grand slam semi-final in a row.

Federer is on 1.25 to beat Djokvic, who is on 4.7 to pull off an upset with Betfair. Federer remains on 1.63 with the same bookmaker to win the event.

However, Rafael Nadal has been showing no ill effects from an ongoing abdominal problem, and also seems to have overcome previous knee trouble.

He faces Chilean Fernando Gonzalez in the quarter finals today, and is on 6.00 to win the Tournament with Betfair.

It was thought either the knee difficulty or abdominal problem could de-rail the Spaniard, but he has looked more comfortable recently. Nadal said of his recent knee troubles: ""I'm very happy after the last two matches I played."

"I had a few problems in those but now I'm in the quarter-finals for the third time in my career here and I'm really, really happy."