The Blaugrana director has made it clear that the Argentine is in high spirits as he continues his recovery from a hamstring problem
The 26-year-old picked up a hamstring injury in Barca's 4-1 Liga win over Betis on November 10 and has since been out of action.
Messi is expected to be sidelined until early January and Zubizarreta has made it clear that his recovery is going according to plan, before adding that he is confident the Blaugrana can cope without their star player.
"Messi’s recovery is going reasonably well and he’s in good spirits," the Barcelona director was quoted as saying on the club's official website.
"He is the best player in the world, but when we don’t have him, the others have to be able to compete, because they’re also among the best.
"Over a season, you need all of them and they always have to respond by playing the top-class football required at Barcelona."
The Catalans are currently preparing for Tuesday's Champions League encounter away against Ajax. They sit top of Group H with 10 points from four games and have already sealed their berth in the round of 16.