Halfback Reynolds and five-eighth Mam were both sent for scans after arriving in Brisbane on Friday following the 22-2 loss to Melbourne on Thursday night at AAMI Park.
They were both injured while chasing Storm winger Xavier Coates in the 22nd minute of the match.
AAP has been told skipper Reynolds is set to miss up to four weeks and could be available for the final round clash with the Storm.
Mam's injury is worse and he is expected to miss more than four weeks.
Incredibly winger Selwyn Cobbo also injured a hamstring and limped off with two minutes left on the clock and he too is a four weeks-plus proposition.
The Broncos have an abundance of halves and hookers on their 2025 roster, giving coach Michael Maguire options ahead of four key games before the play-offs.
Fortunately for the Broncos their 35-year-old hooker against the Storm, Ben Hunt, has played 348 NRL games and 255 of them were as a starting No.7.or No.6.
Against the Storm the Broncos had to move bench utility Billy Walters to No.9 when Hunt moved to halfback but Walters trained in the pre-season as a half/hooker.
Walters also played five-eighth at Melbourne and Wests Tigers before making the dummy-half position his own.
Maguire could move Walters to five-eighth or he could call on one of his three back-up halves Coby Black, Josh Rogers or Jock Madden.
The coach also has the option of replacing Hunt by recalling Cory Paix to hooker. Paix started the season as the first-choice No.9. Blake Mozer and Tyson Smoothy are other hooker/bench options.
The Broncos are spoilt for choice.
Former Broncos captain Darren Lockyer told Channel Nine that the Walters-Hunt combination in the halves was the most likely and he doubted Maguire would take a punt on 19-year-old Black, despite him being earmarked as a first grade regular of the future.
"I think bringing Coby in at this point in time is a huge risk in terms of their chances of winning big games, because he's just a kid," Lockyer said.
"I think Ben Hunt goes to seven and potentially Billy Walters goes to six and you bring in Cory Paix and Tyson Smoothy as your combination of hookers.
"That's probably where I think it sits right now, but at the same time if Madge (Maguire) is thinking differently, Coby is an option to try and get an understanding of how good he is."
The Broncos are on 28 points and will need one more win at least to play finals. They play cross-town rivals the Dolphins next week, followed by Newcastle and North Queensland away and Melbourne at home.
Maguire said it was a "crazy" night for injuries with three stars lost to hamstring complaints but added it was not all doom and gloom.
"We'll be right," he said.
"We've got people in the background that can come in.
"That's part of the progression. We've been able to bring a few people in and change around the team a little bit, so we'll work through that throughout the week."
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