Juventus defender Giorgio Chiellini has been diagnosed with a muscle tear in his left knee after lasting just 11 minutes of Sunday's 1-0 defeat to Serie A title rivals Napoli.
The Italy international had to be replaced by Stephan Lichtsteiner early on in a match that was settled by a 90th-minute Kalidou Koulibaly goal in Turin.
Juve boss Massimiliano Allegri was unable to provide a clear update on Chiellini's condition in the immediate aftermath, but said that he "almost certainly" would not be available for the weekend's game against Inter.
And tests on Monday confirmed that the Italy international had suffered a tear to the biceps femoris of his left leg.
The club have indicated that the 33-year-old has already begun receiving treatment for the issue, but it is likely to bring an end to his involvement in the team's final push for the title.
Juve's defeat to Napoli leaves them just a point clear of the Maurizio Sarri's men with four matches left to play, meaning Chiellini's injury will come as a significant blow to their hopes of holding on for a seventh consecutive Scudetto.
The Bianconeri face Inter, Bologna, Roma and Verona before the end of the season, as well as AC Milan in the Coppa Italia final.
Despite their defeat, however, Allegri remains content that his team still have an edge over their rivals.
"We are still top of the table, we still have the advantage," he said. "There are four games to go, two at home and two away, so we'll see what happens.
"Napoli deserve some credit for their victory, but there were barely any chances. They had to win, we needed to either win or not lose.
"There is another advantage, as goal difference is in our favour and the head-to-head record is even. We have to shake off this match, get ready for the next and that will be very important."