Manuel Pellegrini has urged West Ham's disgruntled fans to lay off Marko Arnautovic.
The Austrian forward's form has slumped since he tried to engineer a move to China in January.
Arnautovic was handed a new contract to keep him happy, but his relationship with the Hammers supporters has turned sour.
The 29-year-old, who has not scored in eight appearances, was booed off as he was substituted during West Ham's last two matches.
Frustrated Arnautovic even appeared to swear at a fan behind the dug-out after he was replaced during the 2-0 defeat against Everton last weekend.
Arnautovic is still tipped to leave the club in the summer, but Pellegrini insists he remains committed to the cause.
"I don't think anybody can be happy," said the Hammers boss.
"The fans are not happy, me, Marko is not happy, but this happens to some players in a moment of the season when they are not in their best moment. Maybe they need the support more than to punish them.
"Talking with Marko, he wants to do things better. He is absolutely involved with our team, what happened with China is now over and finished.
"If anyone thinks that Marko doesn't want to be here at West Ham, they are wrong. Marko is absolutely involved mentally and physically.
"I repeat, he is not in a good moment but, supporting him, he will return to what he demonstrated some months ago.
"A lot of players at parts of the season have bad performances. It is not easy maybe to know that you don't have the support of the fans that he had six months ago. But with his work and a positive mentality he will return."
Pellegrini branded the Everton defeat West Ham's worst performance of the season, dealing their hopes of finishing seventh, and a potential Europa League place, a major blow.
Pellegrini is looking for a reaction when they head to Chelsea on Monday night.
"Nobody was happy after the game," he added. "But we will try to finish this season as high as we can in the table. We are trying to involve all the players in that mentality."