The Argentine made his return from injury in the draw with West Ham United on Saturday, only to injure his hamstring and be withdrawn at half-time.
"It depends on the injury, 10-15 days is the minimum," Guardiola said ahead of Tuesday's Champions League clash with Marseille.
"If it's a little bit longer it will be three weeks, one month."
"Kevin is back again, he played a few minutes at West Ham," Guardiola added.
"Aymeric is back, Nathan [Ake] is so close, Gabriel is a week to 10 days to returning. The rest will be two or three weeks - Sergio and [Benjamin] Mendy."