Everton manager Roberto Martinez has leapt to the defence of John Stones, who has been criticised for his erratic displays in recent weeks.
The 21-year-old centre half, subject of a big-money transfer bid by Chelsea in the close season, has been a regular feature in an Everton rearguard that has conceded a Premier League-high 22 goals at home this season.
The young England international was attacked in the media for his performance in last week's League Cup semi-final defeat by Manchester City.
He was also at fault for the opening goal as Everton lost 2-1 to Swansea City last month and conceded a last-minute penalty in a 4-3 reverse at Stoke City's hands in December.
"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 said.
"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."
Martinez was speaking after Everton sealed one of the costliest signings of the mid-season window when Oumar Niasse joined in a STG13.5 million ($A27.45 million) move from Lokomotiv Moscow on Monday.
The manager said the Senegal striker was not bought to act as a deputy for Romelu Lukaku who has scored 15 league goals this term.
"He is not back up. He has his own ability and is someone who can stretch a defence," Martinez said.
Everton, who are 12th in the table, host third from bottom Newcastle United in the league on Wednesday.
Reuters