Tests have confirmed that Juventus vice-captain Giorgio Chiellini will spend three months on the sidelines after tearing his calf.
Chiellini, 28, suffered the injury in training and comes as a huge blow to Juve who only this week cancelled the contract of Brazilian defender Lucio.
A statement on the club's official website said: "This morning Giorgio Chiellini underwent an ultrasound scan at Turin's Istituto di Medicina dello Sport medical centre.
"The scan revealed a tear in the defender's right calf. He will begin his rehabilitation programme, defined by the club's medical staff, over the course of the next few days."
Conte's men, who lead Serie A by seven points, face Cagliari on Friday night before a two-week winter break begins.
He told the club's official website: "It's a shame Chiellini's injured, he's a player everyone would like to have, for what he offers both on and off the field of play.
"He's one of our leaders. But I'm convinced he'll come back stronger than before, looking to recover as soon as possible with the help of the club's medical staff."