Gerard Houllier is confident Nigel Reo-Coker will stay in control of his temper when he visits former club West Ham on Saturday.
Reo-Coker was involved in an angry exchange with Joey Barton during Aston Villa's 1-0 home success over Newcastle last weekend.
He can expect a hostile reception from Hammers fans, who have never forgiven him for leaving Upton Park nearly four years ago in an £8million switch to Villa.
But Houllier fully expects the former England Under-21 captain to keep his cool, saying: "I didn't see that (the Reo-Coker and Barton spat). But I think Nigel will make a demonstration of composure tomorrow.
"Of course, I understand that he has fire in his belly but he must have ice in his head too. That's what makes you a winner.
"How can you be clear and analysing the opponents' weaknesses and posing problems if you're heated? You can't. If you want to control the opposition you have to control yourself first.
"Nigel has improved this side of his game. His overall game has improved.
"People tell me supporters have long memories but Nigel is a man now, not a kid.
"He will be all right. I think that he will be able to prove that he can cope with that."
Houllier brought Reo-Coker back into Villa's first-team plans immediately after taking charge seven months ago.
He said: "Nigel has got character. Whether he plays or not, he's good in the dressing room, he's a team member of the squad.
"He's improved all-round as a player and as a man.
"We don't have many players like that who can win the ball back.
"He's a very committed type of player, he doesn't miss training and he's never injured."
Houllier also gave his backing to Jean Makoun, who impressed in his early games for Villa after joining from Lyon in January but has struggled more recently.
Reo-Coker will be partnered by Villa skipper Stiliyan Petrov against West Ham but Houllier insists Makoun can still be a key player for the club once he fully adapts to life in the Premier League.
"You know that Nigel and Stiliyan are playing tomorrow," he told reporters.
"As for Jean, it takes time to adjust to the pace. I was speaking to Stiliyan when he came from Scotland (Celtic) and he said it took him time to adjust to the pace of the game and the physical aspect.
"Maybe now is the time to give Jean a little break and a rest. I think maybe we will see the best of him next season."