Ruben Loftus-Cheek will have surgery to repair a ruptured Achilles tendon, Chelsea have confirmed.
The England midfielder suffered the injury during the Blues' 3-0 friendly win over New England Revolution in Boston on Wednesday.
Loftus-Cheek has hit a rich vein of form over recent weeks but will miss the Europa League final against Arsenal in Baku at the end of this month as he begins a long road to recovery.
England manager Gareth Southgate had already left 23-year-old out of his squad for the Nations League Finals earlier on Thursday.
We're all with you, @rubey_lcheek.
— Chelsea FC (@ChelseaFC) May 16, 2019
"I went to bed last night and Ruben is in the squad and playing brilliantly and now it is a huge disappointment for him. He misses now a major European final and a brilliant opportunity with us," Southgate told reporters.
"In particular he has really come on in the last few months and looked strong and playing with a lot of confidence and I am really disappointed for him in particular."
Loftus-Cheek scored 10 times across 40 appearances in all competitions for Chelsea this season.
His team-mate for club and country, Callum Hudson-Odoi was struck down by a similar injury during last month's 2-2 Premier League draw against Burnley.