Pete Sampras expects Roger Federer to pass his record of 14 Grand Slam titles and believes the 25-year-old Swiss could almost double his current tally.
Sampras will play in an over-30s series later this year
Federer took his total to 10 with his most recent triumph in Australia.
"Looks like it's going to happen," said Sampras. "I see him passing me in the next couple of years and even taking it to 17 or 18 majors.
"I don't see two or three guys really threatening him. I think he's just going to get better."
Sampras won seven Wimbledon titles, two Australian Open crowns and five US Open titles, the last of which came in his final match in 2002.
I feel like my game is too big to be dominated by someone
"I thought it would take longer than seven or eight years [to break the record]," said Sampras.
"I did think 14 would be a tough number to surpass but he just kind of came in at the right time.
"He's playing tremendous tennis. I don't see him stopping now. Guys are going to have their moments against him but I just think he has got that extra gear that guys don't have.
"Even when he is not playing that well he just seems to find a way to win. I don't see anyone really pushing him.
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"I just see him winning 17, 18, 19 majors. He has 10 already and he's in the middle of his career.
"It's just amazing what he has been able to do and how consistent he has been able to keep it up."
However, the American believes that in his prime he could have held his own against the Swiss.
"I don't think one guy would have dominated the other," said Sampras. "I think our games are pretty similar. It would have been a great clash to see us in our prime.
"Roger is doing what I never did; dominate the way he is. He's lost five matches in two years, that's unheard of.
"But I feel like my game is too big to be dominated by someone. When my game was on, my serve was on, I felt I was tough to beat. I felt unbeatable."