Chelsea midfielder Marco van Ginkel will be out of action for six months after undergoing knee surgery.
Van Ginkel, an £8.4m summer buy from Vitesse Arnhem, lasted just 10 minutes of his full debut after tearing an anterior cruciate ligament.
The Netherlands international, 20, landed awkwardly under pressure from Swindon's Alex Pritchard early on in Chelsea's third-round League Cup win.
Chelsea said that Thursday's operation was a success.
Team-mate Michael Essien tweeted his support: "Stay strong Marco...you will be back stronger."
The Chelsea number 16 starred for Netherlands in this year's European Under-21 Championships, having already made his full senior debut last year.