Clarets winger Robbie Brady is expected to be out for the rest of the season with the knee injury he sustained at Leicester City on Saturday.
Scans have revealed he has torn a tendon in his left knee, suffered after a challenge on Foxes centre back Harry Maguire, which saw his standing leg fall awkwardly.
Brady was stretchered off with his knee in a brace and went straight to hospital, and further assessment has confirmed boss Sean Dyche's worst fears.
Dyche said: “Robbie will have surgery to repair a patellar tendon tear and will be out for a substantial recovery period.
“He will be given all the time and care he needs on his recovery and supported throughout from all of us at Burnley Football Club.”
His absence will be a blow, as the Republic of Ireland wide man - who became the then-club record signing in January this year, arriving from Norwich City for £13m - had hit a rich vein of form, including scoring the second goal in the 2-1 win at Bournemouth last Wednesday.
Burnley were expected to be in the market for a winger in January, and that need has been amplified.
Scott Arfield is expected to deputise against Watford at Turf Moor on Saturday.