Sunderland's nine-goal leading scorer is already regarded as a major doubt for the game against Wigan at the DW Stadium on Saturday, but Bruce will have to sweat on his availability until later this week.
Related ArticlesBolo Zenden: Sunderland must beat 'unfashionable clubs'Darren Bent determined to win World Cup placeSunderland 1 Arsenal 0Steve Bruce backs up referee complaintsPremier League tableSport on television"Darren has gone away for a scan and we're not expecting the results back until Thursday or Friday, but there is a real worry that it is a hamstring strain," Bruce said.
"If that turns out to be the case, then we are looking at losing him for a minimum of three weeks. We will not know anything until the results comes back so we will have to keep our fingers crossed."
There has been a suggestion Bent may have suffered a severe bout of cramp, rather than hamstring damage, but if, as expected, a strain is diagnosed, it would mean he would miss out on the upcoming matches against Wigan, Fulham and Portsmouth.
It would also put a question mark over his chances of facing more challenging games against Aston Villa and Manchester City before Christmas.
A lengthy lay-off would also weaken his chances of winning a place in the England squad for next summer's World Cup finals, as he strives to make up for a disappointing showing against Brazil earlier this month.
Sunderland will be without Bent's fellow striker Kenwyne Jones on Saturday as he completes a three-match ban, but former Manchester United forward Fraizer Campbell could be handed a starting slot.
"It's something we will have to look at, but remember Darren isn't ruled out at this stage," Bruce added. "But we do have options and Fraizer Campbell is certainly a player who deserves a chance up front."
Northern Ireland striker David Healy will come into contention for the trip to Bruce's old club Wigan, as will Irishman Daryl Murphy, when they take on a side looking to bounce back from a 9-1 drubbing by Tottenham.