Mayo have confirmed that Tommy Conroy has sustained a cruciate ligament injury.
The Neale forward suffered the injury just before half-time in NUI Galway's Sigerson Cup meeting with Letterkenny IT in the quarter-finals of the Sigerson Cup.
Conroy had to be treated on the pitch after the half-time whistle blew, before eventually being helped off.
"I really feel for him," said NUIG manager Maurice Shanahan after their win, "It should have been a free in to us, he was fouled and he injured his leg.
“These things happen, it is winter football and I just want to wish well and hopefully it’s not too bad. Our thoughts are with him. It puts a damper on the whole evening."
Mayo confirmed the severity of the 22-year old's injury on Wednesday evening following "a full assessment and examination".
No time frame was placed on Conroy's recovery, although it's unlikely he'll see action for Mayo again this season.
Mayo manager James Horan said, "Tommy is such a great person and player.
"We all wish him well during his rehabilitation.
"Tommy will still play a huge part in Mayo's season and will remain very much part of the panel.
"Unfortunately, injuries like this are part of sport. I know all the players will rally around Tommy and I am sure it will galvanise the entire team, but I know his injury will inspire other players to drive forward, step up and follow in his boots."
Mayo chairman Seamus Tuohey added, "It is such an unfortunate injury at this time of year.
"Mayo GAA however, will provide whatever it takes to support Tommy and ensure he gets the best medical care during his recovery."