A former star of the Ligue Premier was transported urgently to hospital on Sunday before a big match for his club in Serie A.
Ruben Loftus-Cheek was to start during the AC Milan visit to Napoli, second, but he will no longer participate.
The former Chelsea midfielder suffered from abdominal pain cut at night after his arrival in Naples on Saturday.
He was taken to a neighboring hospital where he was confirmed that he had acute appendicitis and needed immediate surgery.
Appendicitis can quickly lead to very serious complications and even be fatal if the appendix becomes so inflamed that it bursts.
Loftus-Cheek only played 12 minutes of series of Serie A since December 6 due to muscle injury.
AC Milan Ruben Loftus-Cheek midfielder was transported to the hospital in Naples on Sunday
He returned to a brief cameo against the Como before the international break, but is now ready for another spell on the sidelines.
The Englishman moved to San Siro de Chelsea in the summer of 2023 and has since contributed 10 goals and three assists in 62 appearances.
Loftus-Cheek received his first league debut by Jose Mourinho at only 19 years old in 2015, in a 1-1 draw against Manchester City.
He spent eight years in the senior configuration and made 33 appearances in all competitions during the 2022-23 season, which turned out to be his last campaign at the club.
On June 30 of last year, Loftus-Cheek finally made the decision to leave Stamford Bridge in search of more minute team minutes and made the permanent passage in Milan.