Thomas, a member of the Gas’ promotion-winning heroes last season, returned to his parent club this summer and has become a prominent figure for the Tykes.
Barnsley however will be unable to call upon his services for a lengthy period after sustaining an injury.
It is suspected that he broke his leg in training as per a report from affiliate website Yorkshire Post, which will keep him out for the next four months.
“He injured himself in training yesterday,” confirmed head coach Duff.
“There was no-one near him but he slid in, caught his legs underneath him with his studs in the ground and ended up breaking his leg and damaging a lot of ligaments in his ankle.
“He’ll have surgery on Tuesday and we’re looking at four months.”
“It’s difficult when players see their mate on gas and air, screaming in agony. "There is a weirdness in the training, players are not really listening because they’re worried about Luke. "I can’t blame that on the performance but it might have been a contributing factor.”
Taking to Twitter to add to the news, Thomas tweeted: “Broken. Today’s news is so hard to take. Thank you so much to the staff, team mates and fans for the support. Working hard to make sure I come back stronger. See you all in 4 months.
In a classy response, Bristol Rovers’ Twitter account said: “Wishing you all the best in your recovery, Luke.”