Andy Murray says it will take time for him to rediscover the pace of the game after a sluggish showing against Roberto Bautista Agut in a one-set exhibition practice match at the Mubadala World Tennis Championship.

Murray stepped in to face the Spaniard in a practice match, as Novak Djokovic cast fresh doubt on his participation at the Australian Open after citing ongoing pain in his right elbow as the reason for his withdrawal.

Former world number one Murray, who has slipped to 16th due to his inactivity, has only played one exhibition match against Roger Federer in November since a hip injury curtailed his season ahead of last year's US Open.

Murray's lack of play was clearly a factor and his usually impeccable movement was missing in a 6-2 loss, in which he slipped to 4-0 down.

However, Murray was glad for the time on court and is keen to keep improving with the Australian Open looming.

"I felt better as it went down, it takes time to get back to that pace," Murray said on court after the knock.

"I felt a bit better towards the end, I need to keep improving for sure. 

"It was nice obviously, I was planning to stay here for a couple of days to get practice, it was unfortunate Novak couldn't play so I agreed to play a set.

"I'm lucky to come out here. Hopefully I can come back again."

Djokovic's withdrawal handed Bautista Agut a walkover into the final, where big-serving South African Kevin Anderson awaits following his 7-6 (8-6) 6-4 beating of Dominic Thiem.