The veteran Inter defender feels his former team-mate could go far and has revealed that he could resume match action within two months
The Argentine played alongside the current AC Milan star between 2007 and 2010 and he has admitted that the Italy international's attitude complicated matters during his time at the Nerazzurri.
"It was difficult with Mario," he told Rai Due.
"If he realised how much potential he's got he could become one of the very best.
"I hope he does, for his sake."
Zanetti, 40, then went on to discuss his recovery process from a serious Achilles injury and revealed that he could make his comeback halfway through November.
"I've started running again – I missed that! I'm still training on my own but I'll have a test on Tuesday and if everything's okay I'll start upping the workload.
"I need to build up the calf muscle a bit. I'm not too far off returning: hopefully it will be around mid-November."