Messi has been ruled out for up to three weeks after suffering a thigh injury during Saturday's 2-0 Primera Division victory at Almeria, a result that saw Barca set a club record of seven successive league wins to start a season.
Four-time world player of the year Messi has, unsurprisingly, been instrumental in that success with eight goals in La Liga already this term and his loss is a major setback for Gerardo Martino's side, but Zubizarreta does not want to use the Argentinian's absence as an excuse, ahead of Tuesday's Champions League clash with Celtic.
"He's a very difficult player to replace," Zubizarreta told reporters as Barca prepared to fly to Scotland.
"We must do without the best player in the world, but we have a squad with extraordinary players.
"The players who are here are very good and we have to play with what we have."
Even with Messi in their side Barcelona were still beaten by Celtic when the clubs met in last season's Champions League at Celtic Park.
Goals from Victor Wanyama and Tony Watt put the home side 2-0 up and although Messi pulled a goal back in stoppage time, it was not enough to prevent the four-time European champions from slumping to defeat.
Zubizarreta is looking forward to returning to Glasgow but insists they are not being driven by thoughts of revenge.
"It's always a pleasure to play at Celtic Park," he said.
"We're expecting a great atmosphere against an opponent who made things very difficult for us last year.
"They showed they knew how to play and knew how to beat us.
"They are very strong on their ground and they look to play with a lot of pressure.
"We know how we must play. Revenge? No. We're going there to enjoy this game, this atmosphere. We'll see what happens."