Roger Federer and Djokovic have both won three Grand Slams this calendar year between them – though it has been a turbulent year for Murray again.
The Brit has found his season plagued by injury issues with the player failing to win a single title in 2018, dropping to a lowly 259 in the ATP Tour rankings.
Muller, meanwhile, has a torrid record against the so-called big four.
He has lost five times against Federer, four against Novak Djokovic and six against Murray.
He has fared slightly better when it comes to matches against Rafael Nadal, who has beaten on two occasions.
Muller is all praise for tennis’ biggest players – though the Luxembourg star has now delved into Federer’s weaknesses.
And he believes the Swiss maestro gives opponents ‘slightly more breathing space’ on court than his rivals.
“I knew that to beat these top players, I’ve had to catch a dream day,” the 35-year-old said.
“I have to admit I’d rather be up against Federer or Nadal than I did against Djokovic or Murray.
“My style of play was just not lying to Nadal on the fast toppings.
“Against Federer, I also liked to play, this, although I could never win a set against him and was mostly without chances.
“Yet Federer sometimes gave you a little breathing space by making some mistakes himself.
“That was not the case with Djokovic and Murray.
“They are so dogged and just don’t give up a point.
“I was always afraid before the game that I could get completely under the wheels against them.”
Muller also opened up on Nadal, adding: “I first met him at a Challenger tournament in 2003.
“That’s where I lost to him in three sets. Many experts had already predicted a great career for him at the time.
“Personally, I had never trusted him to do that. I looked at him more like a small muscle pack that could run from left to right like a whirlwind.
“In our second meeting in Barcelona, I felt something of a fear for the first time on the tennis court – but not necessarily because of Nadal: The local spectators provided an impressive atmosphere on the big centre court.
“Even on the way to the square, we were pushed back and forth by security people. I was very impressed by that. That same year, at Wimbledon, I succeeded with a success against him than the big surprise.”