Ronald Koeman has suggested his Everton side must have a more offensive mentality if they are to get the best out of Romelu Lukaku against the Belgian's former club Chelsea.

Lukaku has been in scintillating form for the Toffees in 2017, netting 13 goals across eight successive Premier League wins at Goodison Park since the turn of the year.

Everton's struggles on the road were epitomised by a poor display in the 0-0 draw with West Ham last time out, though, and they will face a stern test when Antonio Conte's league leaders visit Merseyside on Sunday.

Key to a positive result for Everton will be Lukaku, whose future at the club remains in doubt, and Koeman believes his side need more players who possess the 23-year-old's attitude if they are to compete with the likes of Chelsea - who beat the Toffees 5-0 earlier in the season.

"I don’t know if he [Lukaku] will stay, we will see what happens at the end of the season," Koeman said.

"We like to keep the best players. Lukaku always wants to show the best of himself. I think we need offensively more players who score more goals because the difference between Lukaku and the rest of the players is too big. 

"Maybe we need to change our mentality because I felt a little bit less intensity, maybe less motivation [against West Ham]. 

"It's always difficult if you have the end of the season feeling. That's what I don’t like."