Dean Marney has suffered a cruciate knee ligament injury and will miss the rest of the season, Burnley manager Sean Dyche has confirmed.
The 32-year-old sustained the injury while attempting to tackle Arsenal midfielder Mesut Ozil in the 73rd minute of Burnley's 2-1 defeat at the Emirates last Sunday.
Midfielder Marney was shown a yellow card by referee Jonathan Moss before being carried off on a stretcher and replaced by James Tarkowski.
"Dean's seeing a specialist today [Thursday] but unfortunately he has done his right cruciate, which is the one he did before," Dyche said.
"There's obviously a long period of rehab for that one but he's come through that once before so in a good bad way, he knows the script.
"He knows how long the rehab is but it's a blow for him and a blow for us because he's been playing very well. You don't want to lose any player.
"He's been an important part of what we've achieved here over a number of seasons. He's a tough-minded man and knows he's got the full support of everyone here."
Sky sources understand Burnley have had a £10m bid for midfielder Robert Snodgrass accepted by Premier League rivals Hull City.
West Ham have also had their offer for the Scotland international accepted by the Tigers, while Middlesbrough remain interested despite having a bid turned down.
When asked about strengthening his squad following the injury to Marney, Dyche added: "We were looking to strengthen anyway. I've made it clear we are always looking at the background picture, if you like.
"Quite obviously, we're not the market leaders so we have to be aware of what might change in our own group.
"We don't work with a big number. We're roughly around 20 recognised first-team players and we have to be working constantly to see what's out there, what's available and what fits into our bracket."