Plymouth Argyle manager Derek Adams says the number of bookings Carl McHugh has received is worrying him.
The Irish defender has been yellow-carded six times already this season.
The 22-year-old missed the Football League Trophy tie with Exeter City this month because of a one-game ban.
"Last season Carl was exactly the same, but it's the nature of his game," Adams told BBC Radio Devon. "He's got to be a wee bit calmer and sometimes not make the challenge that gives away a foul."
He added: "It's a concern, but it's important that he doesn't get booked. I've spoken to him about it over the last day or so and I'll continue to.
"You've got to make the right challenge, and if you win the ball then you don't get the booking.
"He's a very good player for us, he's been excellent since I came in here and is a pivotal part of the squad."
Meanwhile, Adams says he will assess the fitness of striker Reuben Reid ahead of Tuesday's match with third-placed Oxford United.
Reid was substituted soon after scoring the winner against Accrington in League Two on Saturday.