Everton boss Ronald Koeman admits he's unsure if Romelu Lukaku will still be at Goodison Park next season.

The Belgium international left Chelsea for £28m in 2014 and the Blues are now keen to re-sign the striker, who has been valued at £100million by the Toffees.

And Koeman has conceded Everton could find it hard to keep hold of their best players this summer.

The Dutchman said: "First of all we like to keep the best players, but that's difficult. I don't know if it's possible to keep them. And then we have to analyse the team what we need to improve the team for next season.

"I think we need offensive-wise we need more players, who score more goals because the difference between Lukaku and the rest of the players is too big.

Asked if he was hopeful of having Lukaku next season, the Everton boss added: "I don't know, we will see what happens at the end of the season."