Cardiff City forward Isaak Davies faces a spell out with concussion after an off-the-ball incident that left head coach Brian Barry-Murphy fuming.
The Welsh club are believed to be disappointed by the lack of action over the incident at Rotherham United that is expected to see Davies miss their next three games.
Davies suffered the head injury in the closing stages of the League One leaders' 3-0 win over the Millers last Saturday.
No foul was given but Bluebirds boss Barry-Murphy described it as a "sickening blow", while players reacted angrily on the pitch.
It has now been confirmed Wales cap Davies, 24, suffered delayed concussion and has been unable to train as he follows protocols.
Cardiff have contacted officials in a bid to highlight the incident but no retrospective action is expected.
Davies is now set to sit out Cardiff's home games against Luton Town on Saturday (15:00 GMT) and AFC Wimbledon next Tuesday, as well as the trip to Plymouth on Saturday, 21 February.
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Barry-Murphy was critical of the standards of League One refereeing after the game at Rotherham.
He also said responses from Professional Game Match Official Limited (PGMOL), the body responsible for refereeing in English professional football, to previous complaints were "not good enough".
Cardiff have been left angered by a run of recent incidents that included an alleged elbow on Ryan Wintle against Stockport County and a neck injury suffered by top-scorer Yousef Salech in the same game.
Salech received lengthy treatment amid fears of serious injury, something Barry-Murphy said had "been coming" because of a lack of protection.
The striker remains absent from the team that go into Saturday's game with Luton Town (15:00 GMT) two points clear of second-placed Lincoln City.
Speaking ahead of the fixture, Barry-Murphy said: "We haven't got a lot of experience with neck injuries, so we have to be patient."