The EFL has asked Huddersfield to explain their team selection after manager David Wagner made 10 changes ahead of Saturday’s 2-0 loss to Birmingham.
The Blues secured only their third win in 24 league games despite being reduced to 10 men after 23 minutes, with Jonathan Grounds’ goal and a Craig Gardner penalty enough to beat the play-off bound Terriers.
The win kept Birmingham out of the relegation zone but angered their fellow strugglers as Huddersfield fielded a much-weakened side.
An EFL statement on Tuesday read: “We have today written to Huddersfield Town to request their observations in relation to team selection during their recent Sky Bet Championship match with Birmingham City.
“As per our regulations, the EFL Executive will refer the matter to the board if it is deemed appropriate to do so.
“It should be noted, however, that the result of Saturday’s game will stand in all circumstances and any potential action would be taken against Huddersfield Town directly.”
Huddersfield cannot finish lower than fifth in the table, although victory on Saturday would have kept them on course for third. The defeat left them below Reading and Sheffield Wednesday as the playoff field takes shape.
Wagner said after the match that the selection was in line with his rotation policy.
“At Wolves I made five changes and everyone knows my rotation policy is part of my idea in a busy Championship,” he said.
“Changes were necessary with our thoughts to the playoffs as no one knows what will happen over the next month.
“It is unfair talking about my starting XI because I wanted fresh players.
“At the moment we are not getting consistent results but we have been able to stay in the top six and progress to the playoffs for the first time in 45 years.”
Birmingham’s win put them two points clear of 22nd-placed Blackburn, with the relegation fight going to the final day of the season.