Eden Hazard should not have "taken the law into his own hands" when he tried to retrieve the ball from a ball boy, according to Professional Footballers' Association chairman Gordon Taylor.
The Chelsea midfielder was sent off for kicking Swansea ball boy Charlie Morgan during the Capital One Cup semi-final second leg.
"You can't take the law into your own hands," the PFA chief told BBC Sport.
"He lost his head and had to receive a punishment."
Taylor added: "You can understand the frustration of wanting to get the ball back but his actions were unacceptable and the referee had no alternative."
The Football Association is reviewing footage of the incident.