With regular custodian Reece Walsh on the sidelines with a PCL injury, 22-year-old Cobbo is the only remaining fit top-36 player to have started a NRL match at No.1 - and he's only done it twice.
A season-ending ACL injury to Hayze Perham ruled him out of the equation.
Cobbo will have the ultimate challenge against ladder leaders Canterbury on Thursday night at Suncorp Stadium, where he can expect a working-over from the kicking games of Bulldogs halves Matt Burton and Toby Sexton.
In 2024 Cobbo starred in a 13-12 win over Manly in Magic Round, making 228m from 19 runs with two line breaks and 11 tackle busts with no errors. It was a complete performance.
The previous year in round one in a 13-12 victory over Penrith, Cobbo ran for 192m but also made four errors.
Broncos prop Pat Carrigan has not forgotten Cobbo's magic against Manly.
"I just love playing with 'Selly'. He has done a job for us before," Carrigan said.
"He played there in Magic Round last year and that game speaks for itself, so I have got all the confidence in him that he can do the job again."
There is a view that the speed of the game has made it tougher for fullbacks with a bigger frame such as Cobbo to shine.
The success of pocket rockets such as New Zealand fullback Keano Kini has been noted. Then there are the more active, elusive and fit custodians such as elite No.1s James Tedesco and Dylan Edwards, plus rising stars like South Sydney's Jye Gray.
"I think (Cobbo) will be fine," Broncos prop Corey Jensen said.
"It is a different game and there are a lot more smaller fullbacks, but there is a place for the bigger, mobile fullback (like) Latrell (Mitchell).
"Selwyn has a really strong running game and we expect him to get involved a lot on Thursday night.
"He has been there before and done the job. He is a different kind of player to Reece but has different attributes he will bring to the team. We have confidence he can step into the role."
Meanwhile, Walsh is expected to miss four to six weeks, and Carrigan said it could "potentially" freshen him up.
"You don't want injuries, right, so I don't think you want to be in that position, but it can always be a positive," Carrigan said.
"It gives an opportunity to maybe look at some footy and work on some different things, but a lot of the good things that we've been doing have come off the back of him too.
"I had a break, a longer one, in 2021 with an ACL and it helped refresh and rejuvenate me.
"So if you can take the positives out of it and get better in a little way, then I'm sure he'll be fresh and ready to go when he comes back."
In late selection news, Jordan Riki has been ruled out of Thursday night's clash with the Bulldogs with an infection.Â
Brendan Piakura, who had been named on the bench on his return from suspension, is Riki's replacement in the starting side.
Tyson Smoothy, originally the 18th man, comes on to the bench.
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