Newcastle keeper Rob Elliot could miss Euro 2016 and his club's battle to stay in the Premier League after sustaining a knee injury in the Republic of Ireland's draw against Slovakia.
Republic boss Martin O'Neill described Elliot's injury as "serious".
"It's a real disappointment and obviously a dampener on the evening," said O'Neill after the 2-2 draw.
Elliot, 29, was hurt as he tried to keep out Miroslav Stoch's opening goal in the Aviva Stadium game.
"He was going really well at Newcastle and looking forward to the game and coming here into the squad with a lot of confidence," added O'Neill.
"I have just spoken to the doctor and he's not happy."
Newcastle later tweeted that the full extent of Elliot's injury would be assessed on Wednesday.
Elliot injury could lead to Given recall
Elliot's misfortune further increases the chances of a recall for veteran Stoke keeper Shay Given.
The 39-year-old was working as a TV pundit at Tuesday's game in Dublin and spoke to O'Neill about his own recovery from a knee injury.
Jack Butland's broken ankle suffered on England duty against Germany has increased Given's chances of featuring for Stoke during the club's Premier League run-in.
Elliot has earned praise for his club performances since coming into the team in place of injured Dutchman Tim Krul in October.
O'Neill pleased with Republic performance
O'Neill declared himself satisfied with his team's performance as first-half penalties by Shane Long and James McClean earned the Republic a draw against their fellow Euro 2016 qualifiers.
"We played some nice attractive football, particularly in the first half," he said.
"There were a lot of substitutions made by both teams and that disrupted things in the second half.
"Overall, there were some good performances. The cohesion we had was surprising given how much we had changed things around for this match."
McClean, eager to seal his place in O'Neill's squad, revealed he is a novice at taking penalties.
"I took the second penalty because Shane was a bit sore after taking a knock," said McClean. "I had never taken one before so there was a bit of pressure on it."