Andy Murray's coach Jamie Delgado believes Roger Federer may be carrying a knock as he is abstaining from training before games despite waltzing into the semi-finals of the ATP World Tour Finals in London.

Federer made it three wins from three in the round robin stage of the season-ending tournament, with a victory over Marin Cilic in straight sets. Before the game, when asked about his preparedness, the Swissman revealed that he didn't practise on Wednesday, opting to spend the day with his family instead.

It was a dead rubber for the 19-time Grand Slam winner as he had already made his way into the semis after the second game, which may have encouraged him to take some rest ahead of the knockouts. When asked if Murray would choose not to practise in the middle of the tournament, Delgado said no and suggested Federer could be carrying a knock.

"To me, that's either because he's a little bit tired or his back is giving him a bit of trouble. It would be pretty rare to take a day off during the tournament unless there is some sort of physical issue," Delgado told Sky Sports.

After his triumph at Wimbledon the Swiss star raced to the final at the Montreal Masters, but was beaten in the finals by Alexander Zverev as the former picked up a back injury during the tournament. The injury in Canada forced Federer to withdraw from the Cincinnati Masters and was not at his best for the US Open, allowing Rafael Nadal to triumph.

The Swiss veteran could win seven titles this year, including the Australian Open and a record eighth Wimbledon title to overtake Pete Sampras' seven championship wins.

Roger Federer
Roger Federer will end the year as the world number two behind long-term rival Rafael Nadal Getty
Roger Federer Rafael Nadal Wimbledon ATP World Tour Finals