Darren Cahill a tennis coaching great

Glenn Cullen
It hasn't always been smooth sailing but Darren Cahill is getting the best out of Simona Halep

As Nick Kyrgios and Bernard Tomic struggle with their games and who to turn to next, one of their countrymen has quietly gone on to become one of the great mentors in tennis.

Darren Cahill took a third player to a grand slam singles title on Saturday when Simona Halep finally broke through to win the French Open.

The South Australian had already overseen the rise of Lleyton Hewitt (2001 US Open) before linking with Andre Agassi for an Australian Open title in 2003.

Cahill also took all three players to No.1 in the world.

It says much about the skill set of the 52-year-old former US Open semi-finalist and world No.22 that he's gotten the best out of players of both sexes and at very different stages of their careers.

His work with Hewitt was mostly when in his teens, Agassi's was in the twilight of his playing days while Halep sat somewhere in between the two.

Not that it's been all smooth sailing with the latter.

The pair split in Miami last year after Cahill called out his charge courtside for her habit of self-destructing when the going got tough.

They had re-connected five weeks later during the clay court swing and while Halep would go on to have more near misses - a difficult loss to 2017 French Open winner Jelena Ostapenko and a final defeat to Caroline Wozniacki at the 2018 Australian Open - she became stronger.

"That match also helped her," Cahill said of the grinding three-set loss at Melbourne Park, her third from as many grand slam deciders.

"To know that she can step up on the big stage and play her best tennis, and then - if you're not good enough to win - you shake your opponent's hand and you're pretty damned proud of what you're able to accomplish."

One slam on she got her major breakthrough while Cahill confirmed his status as one of the great motivators in the modern game.

"She showed a lot of maturity; she's grown up a lot in the last 12 months," Cahill said.

"Sometimes the losses do make you mature pretty quickly - you can go one way with your career and go downwards or you can suck it up, work a little bit harder and try to do it again, and that's the way she went.

"This one was special."