Haas will go for scans in the coming days on a medial ligament injury that threatens to rule him out for the next month and perhaps threaten his chances of lining up for NSW in the State of Origin series opener on May 27.
The durable prop clutched at his knee before limping off in the first half at Campbelltown Sports Stadium.
He will join a bulging list of unavailable players that includes Patrick Carrigan (suspension) and Reece Walsh (cheekbone) ahead of next week's meeting with Canterbury.
"Looking across my coaching career, that's up there with one of the great ones," said Maguire, whose side nabbed a 21-20 win courtesy of an Adam Reynolds field goal.
"The way the boys rallied around each other and the togetherness of the group was on display."
As well as facing the Tigers without Carrigan and Walsh, Maguire also had playmaker Ben Hunt, first-choice hooker Cory Paix, his deputy Blake Mozer and utility Billy Walters sitting on the sidelines.
Brisbane's depth at hooker was so badly depleted that Maguire started journeyman halfback Josh Rogers in the No.9 jersey before bringing Cameron Bukowski off the bench for his NRL debut on Saturday.
Kotoni Staggs battled through a foot issue while fill-in fullback Jesse Arthars picked up a cork under heavy fire from the Tigers' kick chase and failed to see out the match.
Regardless of who was out there, what pleased Maguire most was how his depleted side never surrendered as they deprived the Tigers of a fourth-straight NRL win for the first time in 14 years.
"We had so much going on….The way I've seen the group developing and what they've faced over the last 16 months - that's the character of what I see," Maguire said.
"Amongst all the madness that might go on around the team, that's what I get to see quite often."
Paix is expected to be cleared from concussion but appears the only Broncos player likely to return to face the Bulldogs on Friday.
Maguire will rely heavily on prop Xavier Willison, who punched out 142m on Saturday, without his first-choice front-row duo in Haas and Carrigan.
"I've got players that are growing and Xavier was excellent," Maguire said.
"He played plenty of time and saw one of his good mates in Payne on the sideline and he had to roll his sleeves up."
