Leicester City midfielder Richie Wellens could be out until the early stages of next season after suffering a cruciate knee ligament injury.
The 32-year-old, who limped off against West Ham on Monday, has a partial tear.
"If surgery is involved we could be looking at September or October. But if it is treatable, he could be back for pre-season," said boss Nigel Pearson.
Meanwhile striker Jeffrey Schlupp needs an operation on a knee injury next week, but should be fit for pre-season.
Pearson added: "He [Schlupp] will have surgery next week on his other knee. He's had a bit of an unfortunate season. He has had two injuries to his knees.
"We have to get the surgery done and get the rehab right so he is ready for pre-season."
And although Pearson said Wellens injury prognosis was a big blow, he said they were waiting for more news before ruling him out of pre-season training.
"His knee is fairly stable so it could be that we treat it conservatively, but we will have to wait a bit longer to get the final prognosis on how we take it forward," he added.