Stefan Edberg is pleased with Roger Federer's form despite Federer's having failed to add to his 17 grand slams.
Edberg, 48, became Federer's coach in December 2013 and admits it has been a learning process for both parties.
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He believes Federer is in fine form heading into the U.S. Open, which begins Aug. 25 in New York.
"The great thing is he's played some really good tennis this year and he's back playing some really good tennis again," Edberg told a teleconference on Tuesday.
"I think if Roger is still in the game, it's great for tennis."
Federer is third in world rankings after slipping to as low as eighth earlier in 2014. He has a record 17 grand slam titles, but the most recent of those came at Wimbledon in 2012.
He reached the semifinals at the Australian Open and title match at Wimbledon without clinching an 18th. Still, Edberg said, Federer could still beat anyone.
"The way he's playing now, he's a threat to anyone out on the tennis court," Edberg said.
Edberg said he was surprised to receive the call from Federer during 2013, enquiring about his availability to coach.
"It was never something that I thought that I ever would do, to be honest," he said.
"I had a phone call last September or October. I had a call from Roger that he was looking to find somebody else.
"It took me by surprise. It took me some time to decide but I felt I needed some time to think it through."