World No. 1 Novak Djokovic just turned 34 on Saturday, but he’s nowhere close to the end of his reign, according to four-time Grand Slam champion Jim Courier.

After winning the Australian Open in February, Djokovic enters next week’s French Open with 18 major titles. Rafael Nadal, who turns 35 on June 3, has 20 career Slams, as does 39-year-old Roger Federer, who will play just his third event of 2021 in Paris following two knee procedures in 2020. But in the long run, Courier likes Djokovic to finish atop the all-time men’s Grand Slam leader board.

“I definitely think Novak will have more bites at the apple, assuming that both [Nadal and Djokovic] stay healthy,” Courier said in response to my question Wednesday on a Tennis Channel conference call. “I think he’s a little bit more viable across the other surfaces. If you look at the balance of [where] their majors have been won, I think that’s probably true given that three of the four are not on clay.

“It’s hard to see Rafa not winning at least 2-3 more based on how healthy he is right now and how much of a prohibitive favorite he is at Roland Garros so if he punches out to 22-23, Novak has a lot of ground to make up but he seems to be likely to have a longer career. He’s a year younger and he tends to be in pretty good health and as long as he can stay away from the operating table and stay focused, I think he can be viable until he’s 40 years old. “

If the Serb wins, say, two majors a year for the next six years, that would put him at 30 career Grand Slam titles — an absurd number considering Pete Sampras was the men’s leader with 14 until the “Big 3” came along. Even a more conservative estimate would put Djokovic somewhere in the mid 20s.

Even if Djokovic doesn’t win the French Open for a second time, he will be the favorite at Wimbledon which he has won five times, and the U.S. Open, where he has won three titles. It’s not outside the realm that each of the “Big 3” will have 20+ majors at the end of the year.

Djokovic has made no secret of his desire to finish atop the all-time list, pointing out that so called “young guns” have yet to knock off the “Big 3.” Djokovic and Nadal have won 10 of he last 11 major titles.

“Everyone talks about the new generation coming and taking over us, but realistically that isn’t happening still,” Djokovic told Eurosport before the Australian final.

“We can talk about it all day but with all my respect to the other guys, they still have a lot of work to do. I’m not going to stand here and hand it over to them. I’m going to make them work their ass off for that.”

As for the French Open, Courier, like just about every else, sees Nadal as the favorite to capture his 14th Roland Garros title and record-breaking 21st major. Nadal is coming off beating Djokoivc in three sets in the Italian Open final, and Djokovic hasn’t beaten Nadal on clay in five years.

Djokovic is competing this week in the home country at the Serbia Open, where his brother Djordje is the tournament director.

“There’s a few things to look to if you’re Novak and be optimistic about but of course Rafa has the reason to be the most optimistic of all,” Courier said of the French Open, where the draw will be unveiled on Thursday.

And although Djokovic was defaulted in the fourth round of the U.S. Open last year for accidentally hitting a lineswoman in the throat with a ball, Courier feels Djokovic needs to bring his passion to compete with Nadal and others at the French.

“Emotional Novak is the best Novak from my point of view,” Courier said. “I think in the time when he had the elbow troubles and he seemed to be less engaged mentally, more calm on court, the peaceful Novak wasn't the warrior he needed to be.

“There's a balance there. Obviously we all saw what happened in New York. He has to kind of control the fire that burns brightly within him. If he doesn't have that fire going, he's not the same player.”

As for the long-term picture, Courier likes Djokovic to finish first but isn’t discounting Nadal’s hunger and passion for the game.

“It’s amazing that he’s going so strong right now given the toll that his style of play takes on his body,” he said. “And it doesn’t matter what I think, all that matters is what they do and we’re just lucky to get a chance to watch it.”