Darren Cahill is Jannik Sinner's coach. He was instrumental in getting Sinner over the hump to become a maiden Grand Slam champion at the 2024 Australian Open.
Cahill is an experienced coach and has a great track record of coaching players who win Grand Slam champions while working with him. Sinner is his fourth player to win at least one Grand Slam. Does this achievement make him the greatest tennis coach of all time?
The short answer is yes. After reviewing his resume, he has winners in both the ATP and WTA. Before Sinner, he was Simona Halep's coach. Before that, he was the influence behind his Australian compatriot Lleyton Hewitt and Andre Agassi.
The only coach remotely close to achieving what Darren Cahill has is Brad Gilbert
If you are asking yourself if Brad Gilbert should be in the GOAT coach conversation, the answer to this question is also yes. Gilbert is the only one who has come close to mirroring Cahill's achievements. Gilbert has gotten his success from coaching generational American players, Andre Agassi (early in his career before Cahill coached him), Andy Roddick, and Coco Gauff.
Like Cahill, Gilbert has achieved success with players on both ATP and WTA players. Because both of them are currently successfully coaching younger players, Sinner is 22 and Gauff is 19, it does not appear as though they are jumping ship and moving on to coach another player anytime soon.
There are many similarities between these men. Neither won a Grand Slam as a professional player though both were fixtures on the ATP Tour for more than a decade. Both are close in age, Cahill 58, and Gilbert, 62, and work as ESPN tennis analysts. Neither shows any sign of quitting the game soon. For all of the above reasons, Cahill is the current GOAT among tennis coaches.