After missing much of the season as he recovered from an ACL injury sustained at the end of last year, Staggs returned just a few weeks ago in a stirring Brisbane win over the Cronulla Sharks.
The Broncos managed to pick up a win over the Cowboys on Friday night, but Staggs was taken from the field just four minutes before the full time with a knee injury.
It's now been revealed it's a high-grade MCL injury on the same knee that he injured his ACL on last year.
Broncos head of performance Dave Ballard said the injury was likely to end the season for Staggs, meaning he will finish it having played just four games.
“Kotoni has a high-grade MCL injury after suffering an impact to the knee in a tackle in the second half, and he is unlikely to return to play for the remainder of the season," Ballard said.
“It’s the same knee that he injured last year but it’s important to be clear that his ACL is fine and the injury is localised to his MCL."
It's horrendous news for Staggs, with the Broncos desperately attempting to steer clear of the bottom of the table.
In other bad news at Red Hill, Jake Turpin picked up a high ankle sprain which will see him sidelined for three to four weeks.