Shane Duffy is a doubt for the Republic of Ireland’s Euro 2020 qualifiers against Georgia and Switzerland next month after picking up a calf injury.
Duffy was forced off in the second half of Brighton’s Carabao Cup defeat by Aston Villa on Wednesday night.
Richard Keogh has been ruled out for the season with a knee injury sustained in a crash that led to two of his Derby County team-mates being arrested.
The Republic sit top of Group D after five games.
Brighton boss Graham Potter said Duffy, 27, would be out for “weeks rather than days” with Mick McCarthy’s side travelling to Tbilisi on 12 October before playing the Swiss in Geneva three days later.
“It’s a blow for Shane and we will miss him,” added Potter.
Duffy has been ever-present in the Republic’s defence for their Euro 2020 qualifying campaign and scored in June’s dramatic draw against Denmark in Copenhagen.
The injury to Keogh, who has been Duffy’s defensive partner in all five of the Republic’s Group D games, leaves McCarthy with a centre-back crisis going into the qualifying double-header.