Pete Sampras has described a resurgent Roger Federer, who this season became the first man to win eight Wimbledon singles titles, as "one of those freaks of nature who comes around once every 50 years".

In an exclusive interview with Wimbledon.com, Sampras suggested that Federer, who turned 36 in August, has taken his tennis to new heights this season, including adding a more aggressive edge to his game.

"Roger's had a magical year, to be able to play at this level at his age. He's still playing at a very high level. What Roger has done is improved. He's added aggression to his game, he's coming in, and he's adding things," said Sampras, who, as a winner of seven Wimbledon singles titles, shared the Open era record with Federer until just four months ago.

 Federer's remarkable comeback year began with victory at January's Australian Open, where he won his first Grand Slam for five years. Victory in the gentlemen's singles at Wimbledon took Federer to 19 major titles. All year, Sampras has been astonished at his friend's continuing energy and enthusiasm for the tennis life.

"Physically and mentally, to keep it going at his age, and to want to be out there, that's incredible. He's still happy to put in the time," said the American.

"Roger's just one of those freaks of nature who comes around once every 50 years. He's been very smart with his schedule and hasn't overplayed. He's been playing enough to keep it fresh. He still enjoys the travel. He loves the game. Put that all together and he can play for another year or two if he wants to, and if not, he's got the right to do whatever he wants." 

If Sampras was surprised by Federer's run at Melbourne Park, he wasn't shocked that the Swiss won Wimbledon. "To come back after being out for six months and to win a major, that's a pretty incredible feat. I think we were all surprised that he won the Australian Open because he was coming back after a long lay-off and that's a tough tournament to win, because of the court and the heat."

"But Roger's Roger, he's a freak of nature and he can do things that no one else can do," he said.

"If I was surprised that Roger won the Australian Open, I wasn't that surprised he won Wimbledon just because of the surface and his experience.

"When he's playing well and feeling good, he really should win Wimbledon every year. He had run into Novak Djokovic in the final a couple of times in recent years, and he didn't have to play him this time. And who else can beat Roger on grass? There's really no one."

When Sampras retired after the 2002 US Open with 14 Grand Slams titles to his name, he imagined that his record would stand for a long while.

It was only seven years later, on Wimbledon's Centre Court at the 2009 Championships, that Federer became the first man to score 15 major titles, and this year Sampras' tally has been eclipsed by a second player, with Rafael Nadal winning Roland Garros and the US Open to reach 16 Grand Slams.

"I never saw that coming, that two players would beat my record so quickly. I didn't even think about that when I was done playing. I figured that my 14 would stay for quite a while, though once Roger started to win some majors and was doing it with ease, I was starting to think that he really wanted to do it. And then he got to 10 and was really dominating and I thought he had it in him to get to 20. That's how I really felt. And now he has 19. But I didn't have any idea that two guys would win more slams than me," said Sampras. 

Next year, Sampras could be overtaken by a third man, as Djokovic isn't far behind with 12 majors. "No one saw that coming, with three guys accumulating so many slams. You've got three guys winning 47 slams between them, and that's mind boggling.

"In my generation, it was definitely a lot more spread out with a number of different winners, and we didn't have three guys really dominating as Roger, Rafa and Novak have done - they've been been so consistent for so long," Sampras said.

"It's one thing to be better than anyone, but to not have off days, and to continue winning, that's what I'm most amazed by. Those guys show just up every day and win. It's truly been an amazing decade."