Partick Thistle midfielder Sean Welsh faces at least two months out with a foot injury.
The former Hibernian player dropped out of the team to face Hamilton last week and tests showed he needed surgery to repair the damage.
Speaking ahead of his side's Ladbrokes Premiership encounter with Hearts on Saturday, manager Alan Archibald said: "Sean Welsh went for surgery today on his fifth metatarsal.
"Hopefully it's eight weeks. It's a minimum of eight weeks, it could be eight to 12, so hopefully it's eight."
Welsh missed much of Thistle's first two campaigns back in the top flight through injury but has played 64 times since the start of last season.
Archibald said: "I think his injury tag is well and truly away, he has played the best part of two seasons and he is probably one of our best performers this season. It's just disappointing for Sean, he was in a real good vein of form."
Thistle are looking for a third consecutive victory as they face a Hearts side reeling from an Edinburgh derby defeat but Archibald is wary of opponents who are looking to make it up to supporters following their 3-1 loss to William Hill Scottish Cup holders Hibernian.
Archibald said: "I read their manager's comments and a couple of their players' comments, so we have got to make sure we are on our toes and wary there is not a backlash from Hearts because I imagine they feel they owe their fans one.
"We said before last week's game against Hamilton, they had a midweek cup tie that went to extra-time, 'Can we start the game well and make them feel tired?' And that's what we have got to do again."