Roger Federer eased past Jack Sock in two sets on the opening day of the ATP World Tour Finals on Sunday, then calmed concerns about the playing future of the absent champion, Andy Murray – an upbeat view in sharp contrast to gloomy prognoses by Tim Henman and Andrew Castle.

While Murray’s British friends fear his injured hip could bring his career to a premature close, Federer, who played the Scot on his return from four months off the Tour in an exhibition match in Glasgow on Tuesday, has no such worries.

“Considering he has been totally out of the spotlight, it was a brave move for him to put himself out there, give it a go,” said Federer, who had just beaten Sock 6-4, 7-6 (4). “Nobody really knew how he was doing. I was happy how he was playing. Definitely he can move better, he can serve better. We know all these things. For a start it was quite encouraging and OK.

“He still has a lot of time before Australia comes around. Only he knows at what level he wants to return to competition. But I thought he was actually pretty good. I didn’t expect him to be this good yet.”

Earlier, however, Henman told the BBC: “You see him walking around in between points or away from the court, the limp is quite pronounced. Then when you see him moving on the court, his movement is improving. I still think he’s got a long way to go to get back and be 100%.”

Castle said: “I tried to find out a few things about his hip. The team doesn’t give too much away. He’s doing his best to be ready to go out to Australia and to acclimatise. But, look, I’ve got a metal hip. The hip is bad news. It ties up the top half and the bottom half. You need it. I’m very worried about Andy’s future in the game because of the area that is clearly troubling him. Fingers crossed he will be able to come back.”

Federer, meanwhile, began his pursuit of a seventh title here in impressive style. There were a few mis-hits, some dazzling winners and the result that many among the 20,000 fans present were hoping for against Sock, the American underdog who had to win the final in Paris last week to make the final eight here.

“It was really just a matter of trying to keep the ball in play,” Federer said afterwards of the challenge of defusing Sock’s rocket-like serves after soaking up 11 aces.

“It’s always a struggle early in a tournament. After a while you’re just happy to hit some good strokes. The second set was tight. The breaker could have gone either way but he helped me with a double fault and some mistakes.”

On his performance he said: “I was serving well, didn’t have too many problems in the second set. That was a good win for me, because it was tricky. He served big: 105mph, 110, 115 sometimes on the second serve.

“I’ve been coming over on the return on the backhand for a while, the bigger racket helps, and it’s also about more confidence. I didn’t serve and volley as much I would like today. If you come in, the more time you spend at the net you find the more points there are there. It’s a great option to have. If it doesn’t work, don’t do it.”

The first set came briefly to life in the sixth game when Federer butchered a routine volley at the net on game point – distracted possibly by the American turning his back and showing him his backside. There was an exchange of grins on the changeover but, when serious business resumed, the Swiss completed the job. As Federer observed later: “It looks very easy. I don’t know what happened.”

Sock was more competitive early in the second set before the strain told. A double fault cost him break point in the sixth game, he had to settle his nerves at 4-3 and needed to save twice to hold for 5-4.

Federer held to love, a deft volley at the net then getting him a sixth break point. Sock wriggled out of trouble with his final ace but the end arrived when he double-faulted in the tie-break for the sixth time in the match before slapping a tired forehand long and a fraught contest was done after an hour and a half.