Seamus Coleman has suffered a broken leg after a heavy tackle from Neil Taylor during Republic of Ireland's 0-0 draw against Wales on Friday.
The Everton right-back looked in real distress, with physios attempting to hold his lower-right leg in place, as he was moved onto a stretcher and rushed off the field in the 68th minute.
Wales left-back Taylor was shown a straight red card for the tackle and Ireland boss Martin O'Neill had his head in his hands as his skipper received oxygen and was sent straight to hospital.
O'Neill told Sky Sports: "It's a bad break. Seamus is a fantastic player and character - it's a major blow for the lad, for his club and for us.
"Apparently it wasn't the best challenge in the world - I haven't seen it back - but naturally disappointed. He's gone to hospital and I think it's broken.
"I saw Seamus' reaction - he was holding his leg up and it didn't look good."
Wales boss Chris Coleman said: "First and foremost I think the most important thing is Seamus Coleman. We're told that it's not so good, which we are sorry for.
"Neil Taylor is not really that type of player but, if he's got it wrong... I've not seen it again. He's in the dressing room and he's quiet and despondent.
"It's a tough one for Seamus. Thoughts are with him first and foremost. We hope and pray it's not such a bad one."
Wales' Gareth Bale said: "We never wish that on any fellow professional. Obviously we don't know how bad it is but we wish him a speedy recovery."