All that will change this week when 12-time grand slam winner Federer plays his idol, who has 14 majors to his name, in three exhibition matches across Asia, starting in Seoul on Tuesday.
The Swiss ace should win hands-down given he is at the peak of his powers, lifting his fourth Masters Cup title in Shanghai on Sunday, and Sampras retired from the professional game in 2002.
But the American legend has been working hard on getting back in shape and is unbeaten in three starts on the Jim Courier Outback Champions seniors tour, his first serious tennis since hanging up his racket.
"I'm probably hitting the ball better than I did in my prime because of the (improved) technology," Sampras said last month.
But he did admit that "I haven't quite captured the explosiveness I used to play with. I'm not as limber."
How they shape up, and whether they will be taking it seriously, remains to be seen.
Following Seoul, Federer and Sampras move to Kuala Lumpur on Thursday before ending up in Macau on Saturday.
Tickets are selling fast, with fans relishing a rare chance to see two giants of the game on either side of the net.
Lincoln Venancio, managing director of the Hong Kong-based promotor, Entertainment Group Limited, touts the showdowns as "a real once-in-a-life time opportunity".
"Some fans are comparing this classic to the Muhammad Ali versus Joe Frazier boxing match, to Pele and Maradona playing on the same football pitch or to Van Gogh and Picasso working on the one single painting," he said.
Federer admits he is looking forward to the challenge.
"Ever since I was a child, I would watch, imitate, and emulate Sampras' backhand. And now it's part of my own arsenal," he said.
"It's going to be difficult because I practiced with him in LA this year. He seemed to play very, very well. He's still got the lethal forehand, the great slice and the great serve, you know, the fantastic movement and volleys."
Sampras won five US Open titles and two more at the Australian Open, but it was Wimbledon where he was unbeatable, lifting the trophy seven times.
However, it was his failure to reach the top at the French Open that has kept the 36-year-old from being thought of as the best ever.
Along with his grand slam success, Sampras held the world number one ranking for a record 286 weeks, including a streak of 102 weeks that has now been bettered by Federer.
In all, Sampras finished with 64 singles titles.
Federer, 26, is fast catching up, currently sitting on 53 titles and, with time on his side, should surpass the American's haul.
The two met at competitive level only once in their careers, in the fourth round of Wimbledon in 2001.
Federer won in five sets, effectively signalling the beginning of the end of Sampras' reign as world number one.
Sampras has said he expects Federer to beat his 14 grand slam titles. © 2007 Australian Broadcasting Corporation