Pete Sampras says he has watched in surprise as not one, but multiple players have approached and caught his former record of 14 Grand Slam singles titles.

Sampras broke a mark that had been set before the Open era. But since then, both Roger Federer and Rafael Nadal have hit that number, and Novak Djokovic is catching up. Federer set his own record nine years after Sampras won his then-record13th Slam.

"Roger not only passed me, but he has 17,” Sampras told CNN. “And Rafa has 14, and Novak has 11. Literally three guys who passed me in one decade, or in pretty much 15 years' time. It's incredible. I didn't see it coming."

But forget the Big Four. In Sampras’ mind, it’s down to "the big two,” as Djokovic and Federer are a long way in front.

"Quite honestly, those two are the best players in the world," he said.

Sampras noted Djokovic's dominance in a period of tough competition.

"To beat Roger twice at the U.S. Open and Wimbledon, to beat Rafa at the French,” he said. “…Truly he's one of the greats of all time. He's won 11 majors, he's only 28. If he keeps this up over the next three, four years, he could very well pass me and get to 16, 17.”

The American also suggested that Federer is playing "almost better" than he did when he utterly dominated several years ago.

"With Roger, I'm amazed," said Sampras. “…He's 34 now. He's still ranked two, three in the world. He's competing for majors, he's still playing great tennis.”

He sees a drop in Nadal’s level of play, though he cautioned against writing the Spaniard off.

"He's hitting a lot of short balls,” he said. “He's not as aggressive. He just seems really tense out there, he's nervous. When he's losing on clay that's shocking to me … But it's not over for him. He's too good. He's won too much.”

Djokovic and Federer are No. 1 and No. 3 in the rankings, respectively, while Nadal is No. 5.