Ezra Mam is set to become Adam Reynolds' halves partner for at least the next month at the Brisbane Broncos, with the revelation that Tyson Gamble has suffered a stress fracture in his foot.

Kevin Walters made the surprise call to retain the young gun Mam in favour of Tyson Gamble on Tuesday when he announced his team for Saturday evening's clash with the Canberra Raiders.

It was revealed at the time that Gamble "had some lower leg soreness", but that it would require further investigation to prove exactly what the injury was.

News Corp are now reporting that Gamble has a stress fracture which will rule him out for at least a month, meaning Mam will partner Reynolds for the first time in what could be a look at the Broncos' long-term halves pairing.

Stress fractures are notoriously difficult to recover from, and so while Brisbane are understood to be hopeful of only a four-week lay-off for Gamble, it could well ultimately turn into a longer recovery than that.

NRL Rd 8 - Broncos v Titans

Mam made his debut in place of Reynolds during Round 11, with the star recruit - who has led the Broncos to the pointy end of the NRL ladder - missing two games prior to the bye with "groin soreness."

The young gun, who has been with the Broncos for many years and has been on the radar of many good judges since he was 16, starred in his debut against the Newcastle Knights with a pair of try assists and 114 running metres.

He followed that up with another strong performance against the Gold Coast Titans, running for 134 metres and proving he belongs at NRL level.

His kicking game - which has been virtually non-existent to this point - will continue to take a back seat in the combination with the dominating Reynolds, who himself has been in superb form.

Should Mam continue to excel over the next four weeks, Gamble, who came into the team originally after failed experiments with Billy Walters and Albert Kelly in the halves early in the season, may struggle to win his spot back, with Mam a star of the future and locked in at the club until at least the end of 2024.

The 19-year-old is one of the youngest players in the game to be on a top 30 contract.

It's understood both Kotoni Staggs and Payne Haas are also in doubt for the game against Canberra, while Selwyn Cobbo and Patrick Carrigan are likely to back up.