Everton manager Ronald Koeman says England international Ross Barkley "needs to improve" after being hauled off at half-time on Monday night.
Barkley was replaced by Gerard Deulofeu during the Premier League clash with Sunderland and Everton went on to win 3-0, Romelu Lukaku bagging a second-half hat-trick.
Asked about the decision to replace Barkley at his Thursday press conference, Koeman explained he needs to see more from the attacking midfielder.
"There was a reason to take Ross Barkley off at half-time," said the Everton boss.
"You play a match and analyse a match. He didn't play well, lost too many balls. Players of that quality can't lose those kind of balls.
"I had individual talks with Ross. He needs to improve and we will see at the weekend.
"He understands, we showed him the clips and there is no escape.
"You look to his qualities and he needs to be the key player between defenders and strikers, in a position to create and defensively be part of a team.
"In all aspects, he can and needs to improve.
"It is always possible to discuss his position. I spoke to him and we agree that the best position is in the midfield."
Barkley has started all four of Everton's Premier League matches this season so far, scoring twice.
Everton have equalled their best start to a Premier League season and are third in the table ahead of the visit of Middlesbrough on Saturday.