The veteran Italt international sustained ligament damage in his right knee during Sunday's 1-0 victory over Udinese and will be out of action until the new year.
"Of course Pirlo's injury worries us," Barzagli said to Gazzetta dello Sport. "He is unique in his role and a crucial player for us.
"We will miss him a lot.
"But if Juve want to prove that we can go far in any competition then we need to have a strong group, capable of substituting Pirlo.
"No-one can do things like Pirlo but we have important midfielders that can do well."
Pirlo, who has scored three goals in 13 appearances to help Juve climb to the top of Serie A, will miss three league games and the crucial Champions League Group B meeting with Galatasaray in Istanbul on December 10.
Juve need a win in Turkey to guarantee a place in the knock-out round.