Everton manager Roberto Martinez has insisted that John Stones's recent dip in form is not an "issue".

The centre-back, who has installed himself as a regular in the Toffees' team, was criticised for his performance in last week's 3-1 defeat to Manchester City in the League Cup semi-final.

The England international was also at fault for their 2-1 defeat to Swansea City last month.

"When you reach the level John has you are going to be scrutinised and John understands that. He is working very hard to keep himself fit and to produce his best level," Martinez told reporters.

"He has had an incredible season so far for a young man. He has been through a lot in the last eight months and has been incredibly professional throughout and is growing all the time. It is not an issue."

Stones was heavily linked with a move to Chelsea in the summer, but Everton rejected their advances.