Chelsea head coach Antonio Conte is unconcerned if being substituted makes Eden Hazard unhappy, stating his priority is to win matches.
Hazard missed pre-season after fracturing his ankle while on international duty with Belgium in June, and did not make his first appearance of the campaign until September 9.
The 27-year-old, who last week stated he would commit his long-term future to Chelsea despite reported interest from Real Madrid, has completed a full 90 minutes in just eight of his 28 outings in all competitions this term.
Supporters booed when Hazard was substituted before the hour mark in Saturday's 0-0 draw against Leicester City, but Conte assured he is trying not to overwork the Belgian.
Conte says he took Hazard and Fabregas off because they were tired, and the introduction of the fresh Pedro and Willian helped our attacking play. #CHELEI— Chelsea FC (@ChelseaFC) January 13, 2018
"We're talking about a player that recently had a bad injury in his ankle and had surgery, when you have this type of situation you must pay great attention because you can have ups and downs," he said ahead of Wednesday's FA Cup third-round replay against Norwich City.
"He missed the pre-season with us, too. With him we are trying to find the best way. It's normal that one player can't always be on top form. But my task is to try to improve him and try to put him in the best physical condition and make the best possible decision for the team."
Asked if Hazard agreed with that approach, an irritated Conte replied: "This is not important. I am the coach, I decide. It is not important if the player is happy or not, only here [in England] is there this situation.
"You are very worried about whether a player is happy or not. This is not important.
"My first task is to do the best for the player and for the club, not to make every single player happy. Otherwise we'd risk finishing 20th in the table.
"Every press conference there is always this question about whether I'm worried about making my players happy. No. I'm worried about winning."
After an impressive start to life at Stamford Bridge, Álvaro Morata has struggled in recent weeks and is without a goal in five games.
When things don't go as expected there's only one way... Work hard!— Álvaro Morata (@AlvaroMorata) January 3, 2018
Se nos escaparon los tres puntos... Cuando las cosas no salen como uno espera, solo hay un camino... trabajar, trabajar y trabajar. pic.twitter.com/uBcVFLqEOk
Conte feels the former Real Madrid man needs to have more faith in his ability to bring the slump to an end.
"It's normal when your striker doesn't score, you are a bit frustrated," said the Italian. "He had chances to score. In this period he was a bit unlucky, he has to continue work and improve.
"He has to continue to trust in himself. It is important also that his team-mates trust him. We'll see if this situation can change."