Roberto Martinez has said that the injury suffered by John Stones in Everton's 2-1 loss to Manchester Untied this afternoon could be "serious".

The young centre-back lay prone on the Old Trafford turf after he rose at a corner to tee up a chance for Gareth Barry in added time.

Following a lengthy stoppage, he left the field on a stretcher, and it now looks unlikely that he will join up with the England squad next week.

"John Stones has an ankle ligament problem," Martinez told BBC Sport.

"It's too early to know the extent of it but it must be something serious for him to come off."

The result has left Everton in 17th place in the Premier League.