Barkley sustained the knock while preparing for Everton's Premier League opener at Leicester on Saturday and the England international will undergo a scan in the next few days to assess the damage.

The 20-year-old's absence for the start of the season is a major blow for Everton as he was a key player for Roberto Martinez's team last season and earned a place at the World Cup on the back of his club performances.

It has been widely reported that Barkley could be sidelined for between six and eight weeks, meaning he could be out until the middle of October, missing Everton's opening seven fixtures of the season in the process.

Barkley made 34 league appearances in the league in a breakthrough 2013-14 season, scoring six goals, with his dynamic performances earning rave reviews.

An academy graduate, Barkley had been linked with a move away, with Manchester City and Chelsea rumoured to be interested in the youngster, but he outlined his commitment last month by signing a new four-year contract to remain at Goodison Park.

Having made two substitute appearances and one start for England during the World Cup in Brazil, Barkley would have been looking to cement his place in Roy Hodgson's first team on a permanent basis this season following the international retirement of Steven Gerrard.

But he may be forced to watch from the sidelines as England begin their Euro 2016 qualifying campaign against Switzerland next month after a friendly against Norway.

If he is ruled out for eight weeks, he would almost certainly also miss the Group E clashes against San Marino and Estonia.