The 30-year-old winger ended up in hospital after being hurt in a tackle during Monday night's match against Brisbane Broncos at Thrum Hall.
The injury, diagnosed as rib cartilage damage, is expected to keep him out of action for three to four weeks.
Halifax have four Super League matches left, plus the end-of-season play- offs, and Bentley, due to rejoin the rugby union club Newcastle in September, has not written off his chances of a return.
"I don't usually do too badly with injuries," he said. "If it heals speedily, I am keen to have another game."
Halifax also lost their utility back, Craig Dean, and the captain, Karl Harrison, through injury as they were humbled 54-10 by Brisbane.
The Super League campaign resumed last night when London Broncos, safely through to October's quarter-finals of the World Club Championship, were due to take on relegation-threatened Oldham at The Stoop.
The Broncos have their sights on the championship runners-up position, but they could also help determine the battle to avoid the drop, for last night's game is followed on Friday by a trip to Castleford, who are next to bottom.
Oldham were boosted by the return to fitness of the full-back Paul Atcheson while the London coach, Tony Currie, who ended speculation about his future by signing a two-year contract, decided not to risk Shaun Edwards from the start. The veteran half-back, still bothered by a hamstring problem, was on the bench as Robbie Beazley started a third successive match in a different position.