Steven Defour has been ruled out of the Clarets’ trip to Watford on Saturday as he faces up to a spell on the sidelines.
Defour sustained a hamstring injury during Burnley’s 1-0 win over Premier League champions Leicester City on Tuesday night.
And boss Sean Dyche confirmed he has had to discount the Belgium international from his immediate plans.
Dyche said: “We are waiting on further news. We will let that settle down until we know the length of time he will be out, but it’s certainly not a few days.
"It could be beyond a couple of weeks, we’ll wait and see.”
Defour’s absence will be offset by the deadline day arrivals of new signings Robbie Brady and Ashley Westwood.
Robbie Brady became Burnley's record buy when he signed from Norwich on deadline day
The visit to Vicarage Road may come too early for a start for either of the pair, although both may be involved in some capacity as the Clarets look for a first away win of the season against Dyche’s former club.
The Clarets’ boss, who played for and managed the Hornets, added: “There will be that initial settling in period, which the lads here are fantastic about.
“They have got links here both of them, through some of our players, so we expect them to settle down pretty quickly.
“They are fit and well so they are in contention for what we do, certainly as a squad, because they have both been playing actively.
“They will have the change in the way that we work but generally they are fit and well, so they at least come into the thinking.”