Paul Annacone marvels at the adjustments Roger Federer has made

Roger Federer returns a shot to Stan Wawrinka during their men's singles semifinals match on Day 12 of the 2015 U.S. Open at the USTA Billie Jean King National Tennis Center on Sept. 11, 2015 in Queens. Photo Credit: Getty Images / Maddie Meyer

Paul Annacone has seen Roger Federer close up, in a way few others ever get to do.

Annacone is the former Long Islander who took up teaching after his pro career and eventually found himself coaching American great Pete Sampras. In 2010, Federer took on Annacone, who was with him for his last Grand Slam win at Wimbledon in 2012, then through his injury-plagued season in 2013.

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Now a commentator for the Tennis Channel, Annacone is watching a new Federer, an evolved Federer. At the advanced age of 34, Federer played Novak Djokovic Sunday night for the U.S. Open title at Arthur Ashe Stadium in a match that was delayed for more than 3 hours by rain at the start.

"He's a different player against different competition," Annacone said. "Ten years ago he was a dominant player against players who weren't dominant players. These last few years, he ran up against legendary players . He needed to do something, and after that , where his back really hurt, he worked to improve.

"He has always been diligent about trying to improve, which I think is unique for championship players. They can get stuck in their ways."

The most obvious new wrinkle in Federer's game is the charge and chip he uses on an opponent's second serve. He unveiled the tactic -- recently nicknamed SABR (Sneak Attack by Roger) -- in Cincinnati three weeks ago and incorporated it there in his victory over Djokovic in the final.

"I know he wouldn't have used that seven or eight years ago," Annacone said. "But he knows that as he gets older that to be competitive, he has to do some different things. He doesn't have to change his game a lot, but there are things he can figure out that can be effective for him."

Federer was asked before the tournament to compare himself to the player he was 10 years ago.

"It's hard for me to compare myself to back then because you adjust your game to what's coming your way," Federer said. "I felt definitely five, 10, 15 years ago you had a bit more time once the courts slowed down . . . Now the bigger guys came in and started to hit huge from the baseline, and now you started to have less time, even on the slower courts. So I had to adjust my game accordingly, but I think it was helpful for me to start out on faster courts against serve-and-volley players and not get frustrated by two-shot rallies."

Federer also says his serve is as good as it ever was, and his U.S. Open statistics back that up. He's won 82 percent of his first-serve points and 61 percent of his second-serve points. He was broken only twice in his first six matches, holding serve 80 times.

"Your serve shouldn't go away with age," Annacone said. "When he had the bad back, his serve wasn't as effective, but once it was healed, it worked just fine. [The serve] is one aspect of the game you can control and improve. He's been able to do that."

Federer also believes that a big change in his game is the ability to be consistent from set to set, match to match.

"I used to be famous for not being consistent," he said. "I never thought I could bring it in practice, matches, week in and week out, every year. I knew I could be surprising. But consistency was something for me that was just so far away. I tried to learn , see how they did it."

And that's a major reason why Federer met Djokovic for the 42nd time Sunday night.

"It took me a big mental step and a physical improvement to get to that level to play well," Federer said, "but I'm happy I figured it out at some stage."

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