Leicester's Matty James has been ruled out for up to nine months after suffering a cruciate knee ligament injury.
The midfielder was carried off in the Foxes' 2-0 win over Southampton last week and scans have confirmed the severity of the issue.
He may now not return until 2016, after appearing to catch his studs in the turf, and is set for an operation on Tuesday.
Boss Nigel Pearson said: "He's awaiting an operation which he'll undergo next Tuesday. It's not great news for him but hopefully it'll be a straightforward operation. It'll be based on whatever needs to be done.
"It's a real shame for him because he has done ever so well for us. He missed the end of last season as well so it's always disappointing for individuals.
"The most important thing for him is to get the corrective surgery and, from there, get his rehab right.
"These are never nice injuries to deal with but he is a very popular member of the squad and we wish him a speedy recovery."
James has played 29 games for Leicester this season and made 99 appearances, scoring five goals, for the club since joining from Manchester United in 2012.
James will miss the final two games of the Premier League season as the Foxes aim to seal survival.
They go to Sunderland on Saturday before hosting QPR on the final day looking to avoid any last-gasp drama.
They are 15th in the table, three points above the drop zone, having won six of their last seven games - with their only defeat a 3-1 loss to champions Chelsea.
Pearson added: "Our efforts in this run have made it a more realistic possibility to stay up. I don't think I'll fall into the trap of going into any game thinking the job is done, that's not the case. The game against Sunderland in particular becomes a very important one. It remains a similar message, we want it to be in our own hands and this gives us another opportunity.''
Meanwhile, Andy King is fit to return for the Foxes after a hamstring problem but David Nugent is set to miss the trip to the Stadium of Light with a calf injury.