Luton Town midfielder Alex Lawless has broken his hand by punching a wall at half-time in Saturday's loss to York.
With the Hatters 3-0 down, the Welshman, 28, did not re-emerge for the second half against his former club.
He will be out for about a month and has been disciplined by the club, with the punishment undisclosed.
"He does care and it was against his former club, I can understand the frustration," boss Gary Brabin told BBC Three Counties Radio.
"But his act has now cost us for the next month or so.
"I've spoken to Alex at length, he's absolutely gutted. He understands [the punishment] but we'll be keeping that in-house. He realises he's let us down and he'll be dealt with accordingly."
Lawless was already suspended for the visit of Cambridge United on Tuesday.
Saturday's defeat sent morning leaders Luton crashing from first to sixth in the Blue Square Bet Premier.