Hull KR head coach Tim Sheens revealed Joel Tomkins was "in a bad way" in hospital after his captain suffered a severe concussion during a controversial moment in their 28-14 Betfred Super League defeat at Warrington Wolves.
Former dual-code England star Tomkins, 31, was on the receiving end of a hefty challenge from Blake Austin while lying on the floor during the first half at the Halliwell Jones Stadium.
The Australian stand-off - a 'marquee' signing from Canberra Raiders this season - was sent to the sin-bin by referee Liam Moore and Sheens believes it could warrant further action from the Match Review Panel on Monday.
"Joel's in hospital at the moment - and Joel Tomkins doesn't go to hospital unless he's a sick boy," said the coach.
"He's gone in an ambulance, he's in a bad way and we are concerned for him.
"I think the player concerned may a have a little worry this week but it doesn't help us.
"Although in the 10 minutes he was off we scored a try.
"It's a tough one for referees because he doesn't know he's hit him that hard he has put him in hospital.
"And it doesn't matter if you are lying on the ground or running through, if you get hit flush on the head you are going to have a problem.
"I'm not whingeing about it though - it's difficult for referees but losing my captain and a very influential player in the squad for most of the game was a concern."
However, Warrington coach Steve Price - who saw his side maintain their 100 per cent start to the season - said: "I thought the Blake incident was him just being aggressive and to be honest, didn't see much wrong from where I was sitting.
"But obviously I will have to review it again."
Rovers competed hard and were 8-6 ahead after Craig Hall scored while Austin was off.
But Warrington hit back to take the lead moments before the break when ex-Hull FC winger Tom Lineham scored his 100th Super League try and they were in control for most of the second period.
"We made a game of it and tries just at the end of half-time and full time changed the nature of the scoreboard," said Sheens, with Mike Cooper scoring for Warrington with the final play after Jimmy Keinhorst's 69th minute try had offered hope of a Robins fightback.
"We created opportunities and just didn't finish them and you can't do that against a side of Warrington's ability.
"I'm very happy with the effort; the execution needs to be worked on but against a squad rated to be grand finalists this year then we can hold our head up and know we can get better."