Diego Costa has been warned by Chelsea manager Antonio Conte to channel his aggression on the pitch.
The Spain international, who struggled badly for form and fitness last season, has scored twice and registered one assist in his opening three Premier League games this term.
Conte admires the "passion" shown by the former Atletico Madrid striker but wants him to curb any recklessness in order to avoid being punished by officials.
"Diego is a passionate man and for this reason, sometimes, he risks the yellow card," the Chelsea boss said ahead of Sunday's match against Swansea City.
"I want him to improve in this aspect, I want to have him in all the games, but Diego knows the situation.
"I like it when a player shows his passion for this sport. It's fantastic. We do this work but, for us, it's not work, it's a passion.
"It's important to transfer this to our fans and all the people who watch the game.
"So, yes, I want him to carry on with passion, but the right passion and the right aggression. He must transfer his emotions onto the pitch in the right way. Always."
Chelsea have won all three of their opening league matches under Conte and face a Swansea side low on confidence, following their back-to-back defeats to Hull City and champions Leicester City.
And boss Francesco Guidolin has called on his players to be alert against Costa, and not to allow themselves to be provoked, if they are to earn a result at the Liberty Stadium.
"I like Costa a lot. He's a very good striker and his attitude is important to his game," he said.
"I admire players like him - these are the type I want here at Swansea because they are important in the Premier League.
"But I will tell my players to ignore his tactics. We must think only about playing against him and to focus on him tactically.
"And we will have to play well, together to stop him."