The Serie A giants have confirmed the blow after the Italian pulled out of Thursday's training session, the last one before travelling to Cardiff on Friday morning.
"Massimiliano Allegri's men were put through their paces this afternoon (on Thursday 1 June) in a tactical and technical workout of which Stefano Sturaro played only a small part, the midfield reporting muscle strain in his left thigh," the club have confirmed.
Sturaro, 24, has played 28 games for Allegri's side during the 2016-2017 campaign. However, most of his appearances came from the bench so his potential absence against Real Madrid shouldn't be a major concern for the Italian boss.
The former Genoa star completed the full 90 minutes in the weekend's 2-1 victory over Bologna but Allegri is expected to form a midfield consisting of with Sami Khedira and Miralem Pjanic for the Champions League final. Furthermore, Claudio Marchisio will be also available to face the Spanish champions.
Sturaro, nevertheless, will travel with the rest of his teammates to Wales on Friday as Allegri has decided to include all the members of his squad in the trip.
The former AC Milan boss is expected to give an update on the midfielder's situation during a press conference at the National Stadium of Wales at 4:15pm [BST]. Following that, the Bianconeri will have one last training session on the pitch of the final ahead of completing the preparations to face Real Madrid.
Earlier this week Gianluigi Buffon set alarms bells ringing at the Serie A giants after missing the Monday's training session. However, the captain shouldn't have any problem leading his side against Real Madrid with the legendary keeper hoping to lift his first Champions League crown.
Meanwhile, long-term absentee Marko Pjaca remains on the sidelines after the Croatian international suffered a serious knee injury on March.