Everton's Besic facing six months out

"6 months out! #devastated," the 23-year-old Bosnia and Herzegovina international wrote on his Twitter account.

Besic was forced off by injury just 12 minutes after coming on in Wednesday's testimonial match for Wayne Rooney against Manchester United at Old Trafford.

It is the latest in a series of injuries to have befallen the player, who joined the Merseyside club from Hungarian side Ferencvaros in 2014.

A hamstring injury sidelined him for four months last season and a recurrence of the problem kept him out until March.

Everton, who appointed Ronald Koeman as manager in June, host Tottenham Hotspur in their opening Premier League fixture on August 13.

They play Espanyol in a friendly on Saturday.