Anthony Martial, the France international sustained the injury in Sunday’s 2-1 win against Fulham at Old Trafford.
Tests revealed the 27-year-old had suffered a muscle tear, the club confirmed on Tuesday.
Victory for United on Saturday would secure a domestic double for the club, having won the League Cup in February.
BREAKING: Anthony Martial is out of Saturday’s Emirates FA Cup final against Manchester City due to injury. 🤕 pic.twitter.com/a7tbg8B0Gx— Sky Sports News (@SkySportsNews) May 30, 2023
A win would also deny their city rivals’ bid to match the Treble won by Sir Alex Ferguson’s United in 1999, with Premier League champions City also playing in next month’s Champions League final.
In an injury-hit campaign, Anthony Martial scored six goals and made two assists in 21 Premier League matches this season.
United also had injury concerns over winger Antony, after he was taken off on a stretcher in tears in the 4-1 win over Chelsea.
However, manager Erik ten Hag said on Sunday that the 23-year-old Brazilian will “probably” recover from his ankle injury in time for Saturday’s final.
No Martial? Do something for us kings pic.twitter.com/Q9WL57738I— Trey (@UTDTrey) May 30, 2023
Martial joins Marcel Sabitzer, Donny van de Beek and Lisandro Martinez on the list of sidelined players. Erik ten Hag is more optimistic Antony will be available following his ankle injury suffered in Thursday’s 4-1 win over Chelsea.
Speaking about the Brazilian on Sunday, the United boss told club media: “We’ve all seen how he came off and didn’t look great. But the first assessment is not too bad and a good opportunity he is available for the Cup final next week.”
Meanwhile, Van de Beek was spotted completing ball drills in training on Monday as he continues his recovery from having surgery on a season-ending knee injury sustained against Bournemouth on January 3.