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 settled by a 90th-minute Kalidou Koulibaly goal in Turin.
And tests on Monday confirmed a tear to the biceps femoris, the club revealing the 33-year-old has already begun receiving treatment for the issue.
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.