The former world number one gave a good account of himself against the Spaniard but struggled for his full range of movement on what was a fast surface.
The 30-year-old battled hard towards the end of the contest, but eventually succumbed to a 6-2 defeat in the one-set contest.
After the match, Murray said: "I felt better as it went along - obviously a bit slow at the start. Roberto is one of the best players in the world and when you haven't competed for a long while it takes time to get back up to that pace.
"I started to feel a bit better towards the end, but I'll need to keep improving for sure."
Murray currently plans to travel to Brisbane for his opening ATP Tour event of the season before attempting to challenge at the Australian Open.