Reynolds will go for scans on the injury he suffered in the 40-18 loss to the Sydney Roosters on Friday night, with Walters saying it was potentially season-ending.
Respected Brisbane-based physiotherapist Brian Seeney - known on social media as NRL Physio - said the usual time-frame for a return from a torn biceps post-surgery was 12 weeks, unless there were complications.
That would leave the Broncos' 33-year-old conductor and 2014 premiership winner out of action until at least round 21.
Madden, the club's back-up half, had a minor pectoral injury in round eight against Wests Tigers while playing five-eighth.
Walters said Madden was racing the clock to be fit for next Friday night's away clash with Parramatta.
Utility Tristan Sailor is an option if former Tigers half Madden does not recover, but the Broncos are backing the 24-year-old - seen as the successor to Reynolds - to step up in the wake of the skipper's injury.
"We would prefer for guys to not get injured but it gives us an opportunity to have a really good look at Jock for the next 12 or 14 weeks," Walters said.
"It was a one-to-two-week injury but I haven't had a chance to talk to the doctors about Jock and his return. He would be an outside chance against Parramatta.
"(Sailor) could play a role there for us, certainly. He has got a good football IQ.
"We have been defending him in the front line and he has been doing that at Queensland Cup level. We have got some options but will let the dust settle over the weekend.
"We have got good depth. I'm more concerned about how we played tonight. We need to fix that.
"We will get Adam back I am pretty sure before the year is out, and also Jesse Arthars."
Walters ruled out switching fullback Reece Walsh, who had a poor game against the Roosters, to the halves.
"We will leave Reece at fullback," the coach said.
Jesse Arthars being tended to after breaking his jaw against the Roosters. (Jono Searle/AAP PHOTOS)
Winger Arthars broke his jaw against the Roosters and was taken to hospital. He is set to be replaced by veteran Corey Oates.
Lock Pat Carrigan said the club would be tested, but not daunted, by the injuries.
"We will find out what we are made of. Such is life with footy," he said.
"This happens with a lot of teams and ... it is the next man up.
"We have got a lot of depth at our club and I am confident whoever plays there will do the job.
"There is a footy team here. We just have to iron out a couple of things."
The Broncos had some good news on Saturday, with winger Deine Mariner avoiding a ban after being sin-binned for a late hit on James Tedesco.
