Jason Knight will miss September's World Cup qualifiers following a training ground challenge with Wayne Rooney.
The Telegraph report that Knight suffered an ankle injury after coming off worse from a 50-50 training ground challenge with his Derby County boss.
"Jason will be out for eight to 12 weeks", Rooney told the Derby Telegraph at the weekend.
"He has rocked his ankle. Thankfully he doesn't need surgery but needs the time to make sure he gets his ankle strong again.
"Of course [it is a huge blow], everyone knows what Knighty brings to us, he is a fantastic player, great energy, and he will be a loss, but we have to deal with that."
What Rooney didn't divulge at the time was that he was partially to blame for Knight's injury.
The former Manchester United and England player was taking part in a session at Surrey's Pennyhill Park as Derby were short on numbers. Due to a transfer embargo, they have only nine senior players contracted.
Knight's absence is a huge blow to Republic of Ireland manager Stephen Kenny, who is a huge fan of the 20-year old midfielder.
He's started four of Ireland's last six games, and bagged his maiden international goal in June's 4-1 friendly win away to Andorra.
Ireland's World Cup campaign resumes on September 1 away to Portugal, with Azerbaijan visiting the Aviva Stadium three-days' later. Serbia then come to Dublin on September 7.
The Knight incident continues the bad press for Rooney.
Police were called after photos emerged of Rooney seemingly asleep in a room next to two women emerged.
Wine glasses and several empty bottles can been seen under the chair in which the 35-year old is pictured. Scratches are also visible on his knuckles.