Jack Wilshere's recent ankle injury will keep him on the side-lines for at least three months.
He limped off the field during Arsenal's disappointing 2-1 defeat at the Emirates last weekend, after a tackle from Manchester United centre-half Paddy McNair.
The England midfielder has a reputation for being injury prone and this is yet another problem to add to a growing list for himself and Arsene Wenger, who already has to contend with several key members of his squad on the operating table.
The 22 year-old had surgery this week, and has posted a picture of himself in a cast on Instagram, with the caption: "Ankle needed surgery in the end, went well thanks to the main man James Calder!"
Arsenal face West Brom at the Hawthorns on Saturday's early kick off, and have been buoyed by the return of much-missed centre back Laurent Koscielny who returned to training this week.