Novak Djokovic hired Goran Ivanisevic to attend his coaching training at Wimbledon this summer, and the bond bore fruit.
The Serb won his 16th Grand Slam title at the All England Club and is in the driver's seat to finish the year as world number one.
To do so, Djokovic must win every game on his way to winning the ATP Finals title this week.
But Ivanisevic is still trying to raise the bar even higher than today.
"I think the second serve needed a little work," Ivanisevic told Amazon Prime.
"I think his second serve is better, now he's mixing harder, harder and smoother.
"He is reaching more angles and his volleys can improve.
"In my opinion, when he plays aggressively he is the best in the world. He is not a defender, he is a striker and when he attacks you have no chance."
Roger Federer and Dominic Thiem may want to take note of Ivanisevic's comments as they have not yet played world number 2 in the ATP Finals group stage.
Thiem is the first to rise tonight before Federer and Djokovic face off on Thursday.
"I think he mentioned earlier this week that this was probably his best season, winning at home in Vienna, and of course it was a very important win for him. Indian Wells," Djokovic said of Thiem.
"We know how good a player he is on clay. He has shown he can play equally well on other surfaces."
"He has already established the top 5, the top 10. We don't need to talk about his qualities. The quality is great."
"His dedication, professionalism and work ethic are fantastic, and he's a very nice guy. So all the positive things about him."
"His coach Nico Massu, whom I have known for many years and played against him, too, is a great team and deserves to be here."