Novak Djokovic's coach Boris Becker said a lack of competition has sapped the drive of the world number two.
“He didn’t have any opponents anymore," Becker told CNN. "His time was with [Rafael] Nadal, with [Roger] Federer."
"Andy Murray was always the fourth guy. So he lost a little bit of his opponents."
Becker did not totally count out the abilities of the current world No. 1.
"Murray is showing something he hasn't shown before,” he said.
Becker said that shortage of court time against Nadal and Federer meant that something was missing in the game.
He is already used to playing against Nadal and Federer, so it is indeed a very big change, he said.
Federer and Nadal have had injury concerns this year, Federer hurting his knee at Wimbledon, while Nadal injured a wrist at Roland Garros.
— ATP World Tour (@ATPWorldTour) November 22, 2016
Meanwhile, Djokovic's form has slumped, most recently bowing out of the ATP Finals in the decider against Murray.
Becker said he still believes Djokovic can return to form.
"This could potentially be a turnaround for Novak Djokovic’s 2017," he said of the loss to Murray. "As much as this loss is going to hurt him, it’s probably going to inspire him to be remotivated, re-energised for next year. Maybe it was a good thing in the end.”