Retired Croatian professional tennis player, Ivan Ljubicic, has made an interesting admission on his coaching of Roger Federer in an interview with Gazzetta Dello Sport.

The 39-year-old former pro has been training Federer since 2015, since the Swiss Mestro announced the end of his partnership with Stefan Edberg

Under the coaching of Ljubicic, the most decorated male singles player of all-time has enjoyed a remarkable resurgence, winning three Grand Slam titles, including the recent Australian Open.

Explaining his co-operation with the Swiss player, Ljubicic revealed he has tried to help the 36-year-old without making any big changes to his game and mental attitudes.

"My work with Roger is complicated, it's very complicated to manage to improve such a player," the former world no.3 admitted, as per tennisworldusa.org.

"But the easiness, transferring a simple idea to the player covers an important part".

Federer is the greatest ever tennis player but recently explained how Ljubicic makes him a "better player".

"As a team, we are talking tactics a lot obviously before the matches right now," said Federer earlier in 2018. "I need to be reminded of a few things, but those things can be the crucial ones, you know.

"I feel like he's constantly thinking how he can make me a better player."

Federer is no stranger to praise from his coach, after former coach Paul Annacone revealed what sets him apart from other top players.

"We talk a lot about his body [holding up], but I really think that it’s his peace of mind, his ability to decompress the pressure and expectations and how he handles his brand, that’s his biggest weapon,“ Annacone said.

“I traveled with him for four years.

“It’s unbelievable what he’s asked to do. It’s exhausting. But he’s great about finding ways to not let his energy get drained. He’s also pragmatic about wins and losses.

“The overriding thing is that he just loves to play tennis. It’s what allows his skills to still shine at the biggest moments.”

Ljubicic also spoke about fellow Croatian Borna Coric, who recently reached his best singles ranking of world No. 28.

"They are close," said Federer's coach. "Borna (Coric) already beat (Andy) Murray and (Rafael) Nadal and made Roger struggle a lot in Indian Wells by playing so well.

"But it is one thing to play a match well, to win or to get closer to beating them, but it is another to beat them several times, on the most important stages like Grand Slams."