Everton boss Ronald Koeman has revealed that he has "not been impressed" with Manchester United's style of football this season, and expects the Red Devils to miss out on the top four in the Premier League table.

Koeman's unprovoked attack on the 20-time English champions came in response to a question related to Toffees forward Romelu Lukaku potentially making the move to Old Trafford this summer.

Koeman has claimed that Lukaku would not be taking a step up in his career if he joined Man United, with Jose Mourinho's side "struggling" to hit their former heights.

"I cannot see Manchester United finishing in the top four. Zlatan [Ibrahimovic]'s injury looks bad and when I look at the amount of matches they are having to play this season I can see them missing the top four," Koeman told reporters.

"I have not been impressed by the way they play. They are struggling to decide matches. With Everton we drew twice against United this season and both times there was more in it for us.

"The Europa League is a different calibre than the Champions League. The fact that Man United were struggling to beat a team like Anderlecht proves what kind of season the club is having."

Lukaku, who has scored 24 Premier League goals this season, is understood to be refusing to sign a new deal at Goodison Park as he looks to leave the Merseyside outfit at the end of the 2016-17 campaign.

Man United currently sit two points and one spot above sixth-placed Everton in the Premier League table, although Mourinho's side now have three games in hand over the Toffees.