London - Eden Hazard must deliver more to realise his full potential and help dig Chelsea out of a slump in form, manager Maurizio Sarri said on Wednesday.

Sarri heavily criticised his side's mental strength after they slipped to a 2-0 Premier League defeat at Arsenal on Saturday, labelling his players "difficult to motivate".

However, Sarri's tactics are also under the spotlight as he has persisted with playing Hazard in an unfamiliar centre-forward position over the past month.

Chelsea look set to remedy their striker problem with the imminent arrival of Gonzalo Higuain on loan, who scored 38 goals in one season under Sarri at Napoli in 2015/16.

That should see Hazard return to his favoured role on the left side of a front three, and Sarri wants more from the man voted the second best player at last year's World Cup.

"In this moment, he's more an individual player than a leader," said Sarri on Wednesday.

"He is very important for us, of course, because he is a great player. He always can win the match in two minutes. Sometimes in one minute. But, at the moment, he's not a leader."

Hazard's future is also a source of fevered speculation, with the player refusing to extend his current Chelsea deal, which expires in 2020.

In an interview with France Football this week Hazard again raised the possibility he could move to Real Madrid and admitted he has frustrated all of his previous coaches.

"I think he said that coaches told him that he needs to do more," added Sarri. "I think he has to do more. Because the potential is higher than the performances. He has to respect first of all himself. He has to do more."

And Sarri also acknowledged that Hazard's desire to get on the ball as much as possible has restricted his impact when playing in a central role.

"Eden is at the moment a wonderful player, but an individual player. He is an instinctive player so for him it is difficult to play in only one position.

"He likes very much to go to the ball so for him, I think it is very difficult to play as a striker."

Sarri's public reaction to the defeat at Arsenal has raised questions over his future at Stamford Bridge just six months into his reign in charge.

Chelsea, who are fourth in the Premier League, host Tottenham in the second leg of their League Cup semi-final on Thursday, trailing 1-0 from the first leg.