Recent Republic of Ireland call-up Greg Cunningham faces a lengthy spell on the sidelines after undergoing a knee operation.
On Monday the Preston full-back was included in Martin O'Neill's 39-man provisional squad for next month's World Cup qualifiers against Georgia and Serbia having last represented the country in 2013.
However, a knee injury picked up at Derby the following day will prevent Cunningham from linking up with Ireland as North End boss Alex Neil confirmed the issue was serious enough for him to go under the knife.
Cunningham tweeted that the procedure was a success, stating: "The operation went well. Day 1 on the road to recovery."
"It is a real blow for the player, who deservedly had just returned to the Irish squad after an excellent start to the season," said Neil.
"As I described him after the game on Tuesday night, Greg is a warrior - as illustrated by the fact he wanted to carry on despite having done the damage that now requires an operation.
"I have no doubt he will be back fitter and stronger before very long and our medical team will work closely with him to get him back with us."
Ireland take on Georgia away on 2 September and Serbia at the Aviva Stadium three days later in a pair of vital Group D qualifiers.