Dimitri Payet refuses to play as West Ham take on Crystal Palace
Slaven Bilic is determined to solve the Dimitri Payet "puzzle" after West Ham's star man asked to leave the club.
France international Payet has refused to play against Crystal Palace on Saturday in a bid to force a move away from east London.
His stance has rocked the Hammers prior to a crucial game against their fellow strugglers but manager Bilic is standing firm, saying they will not sell their prized asset.
Payet's former club Marseille have reportedly already had a bid knocked back while Paris St Germain are also believed to be interested.
It is hard to see Payet playing for West Ham again, but despite the stand-off Bilic has not closed the door on the 29-year-old.
"Until he changes his attitude he is out of the team and he's not going to train with us," said the Croatian.
"But we are not going to sell him, not whatsover. I expect him to come back and show commitment and determination to the team, like the team has shown to him.
"Is this my toughest challenge? Don't get me wrong, I'd rather be up there fighting with Chelsea.
"But I was thinking on Wednesday by myself that this, including this new situation, is an unbelievably great challenge for me personally.
"I feel so strong - and I don't like it - but I want that challenge and I want to try and solve this puzzle now. I don't know how to tell you that.
"It's not enjoyable of course but when you have such a big challenge in front of you, it motivates you even more and it gets the best out of you and that's how I feel now."
Meanwhile, Crystal Palace manager Sam Allardyce is desperate to get his first win in charge of the club when they face his former side.
Allardyce became Palace manager on December 23 following the sacking of Alan Pardew and after four games at the helm he has failed to win, with two draws and two defeats in all competitions.
Palace came closest to securing victory against Watford during Allardyce's first game in charge and, looking back, the former England manager can see how important three points could have been.
Christian Benteke missed a penalty with the hosts 1-0 up before Troy Deeney converted a spot-kick to seal a 1-1 draw.
He said: "(Getting a win) is massively important.
"Deep down inside, even though I didn't say it, reflecting on the Watford game it was bitterly disappointing and how costly that draw was.
"The victory we should have gained in that game, with it being my first game would have made everyone a bit more comfortable.
"Yes we got a good performance, yes we should have won but we didn't and of course it was very costly.
"Missing the penalty when we did and now we see we have gone four games without a victory so we see how important it was to clinch that game.
"We just have to make sure that we get it sooner rather than later because the longer it goes on, the more fearful players can get so we need to put that away as soon as possible."
Allardyce was Hammers manager for four years and in his time at the club saw his side promoted to the Premier League by beating his old club Blackpool 2-1 in the 2012 Championship play-off final.
However, the 62-year-old is confident that he can get one over them at their new London Stadium home.
He said: "I think the past is something I don't reflect on very often because the future is the most important thing apart from the fact that I had four exceptionally brilliant years at West Ham, I really did enjoy it and probably one of the reasons I am here is because I loved living in London.
"I look forward to the game, it is my first time at the new stadium so it will be interesting to see behind the scenes and most importantly a result is what I am looking for.
"With the players being in the new stadium, they have got their own fears and we have got to try and take advantage of that if it is a distraction for them.
"If we can put pressure on them, we can certainly try and score the first goal and go from there.
"The lack of familiarity for the players and getting used to the surrounding areas is par for the course.
"It is a difficult job and every team that has moved from an old stadium to a new one finds that but I think they will find that with the squad they have got, they will overcome that but hopefully not on Saturday."