Growing up, master mimic Novak Djokovic aspired to serve like his tennis role model, Pete Sampras. Today, the 14-time Grand Slam champion says Djokovic has grown into an all-surface champion capable of matching his record of six straight seasons as year-end world No. 1.

Sampras held the year-end top spot from 1993-98, breaking Jimmy Connors’ previous record of five consecutive years. Sampras, who is friendly with Djokovic and partnered him in a doubles match against the Bryan brothers at the inaugural Los Angeles Tennis Challenge last month, believes that if the Serbian can stay healthy, he can challenge both streaks.

“I do [think Djokovic can remain No. 1 for years]. I was thinking about that when he won Monte Carlo,” Sampras told TENNIS.com in a conference call with the media to promote the second annual Greenbrier Champions Tennis Classic, on September 21-22. “He could stay No. 1 for quite a while, five or six years in a row. Realistically, if he stays healthy, he could very well do it.”

The 25-year-old Djokovic is on a two-year run as year-end No. 1. But there are major stumbling blocks to a five- or even six-year run, including the physicality of today’s tennis, the fact it’s primarily a baseline game where free points don’t come easily, and the demands of sustaining health and producing the required results.

Sampras, who held the No. 1 ranking for 286 weeks, says Djokovic’s consistency—he has reached 11 straight Grand Slam semifinals and has contested eight of the past 10 major finals—all-surface acumen, and the fact he matches up well with his top rivals are all assets that can help him extend his run at No. 1 for years to come.

“He’s so good. Really, even though the players are great today, I think he really only has to be concerned with a couple of them,” Sampras told TENNIS.com. “Roger and Rafa and Murray are the only ones that can really push him. I see him—if he stays healthy—staying on top for as long as he wants to be. I just think he’s that good. He wins on hard court, he wins on clay, he wins on grass. He’s done it all. I think he can stay on top for as long as he wants to be.”