The Argentine has had his torn Achilles tendon operated on this week.
Shakhtar Donetsk boss Lucescu said: "Zanetti is an extraordinary champion. A true great. He is not just a great player, but a great man.
"He was the one who helped me more than anyone when I was at Inter.
"I have no doubt that he can come back from this.
"There is a risk, but I sure hope he can come back."