After winning the Australian Open, Roger Federer defeated Milos Raonic in straight sets Wednesday to reach the Wimbledon semifinals. He will face Tomas Berdych on Friday, hoping for a crack at his eighth Wimbledon title.

How long can Federer, who turns 36 on Aug. 8, keep this up?

“I don’t know how long,” an awestruck Andy Roddick said on CBS Sports Radio’s Reiter Than You. “People are honestly talking about three or four years still. It’s crazy because it’s not even a crazy thought to think that is a realistic possibility. What he’s done is amazing.”

Federer hadn’t won a Glam Slam title since 2012. Then he stole the show in Australia, beating Rafa Nadal in the final.

“My theory was always he can be top 10 as long as he wants to be,” Roddick said of Federer. “I definitely thought he had fallen behind (Novak) Djokovic. For three, four, or five years, that matchup wasn’t favorable to him. The same with (Andy) Murray, and it’s always been a tough match against Rafa. So I didn’t know if he would win again before the Australian Open this year. Then all of a sudden he gets to Australia, the courts are playing a little bit faster, he gets through a couple tough match-ups, and the guy wins the tournament. He’s been far and away the best player in the world for the start of the season. It’s a joke.”

The best part? Federer might be the favorite at Wimbledon. Murray lost to Sam Querrey in five sets Wednesday, while Djokovic retired from his quarterfinals match against Berdych with a sore elbow.

The path is there for Federer.

“He’s the best talent, the most versatile talent, left in this tournament by a long-shot with those guys out,” Roddick said. “It’s just nuts what Roger’s doing still.”

It’s also nuts that Djokovic has struggled as much as he has over the last year or so. Roddick has a theory as to why.

“I do think if we could all bottle confidence and sell it, we’d all be wealthy individuals,” he said. “What goes on between the ears is a huge deal, and he’s kind of lost that edge. Early in the year, you would see him play matches and it felt kind of flat. It used to be a pretty emotional player. You could watch him for two or three games and you wouldn’t really have to guess what was going on. He’s not the cerebral figure like Roger, like Pete Sampras. He’s more vocal.”

That, however, hasn’t been as apparent this year.

“It all kind of felt monotone earlier in the year, and it’s manifested itself a little bit in kind of struggling to find that passion or that fire,” Roddick said. “We always talk about what’s wrong, but for that five years, to kind of have that every day, that mental edge, go to work, and have the run that he had – we have to give credit there also. That should take a lot out of you.”

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