After making his debut in round one, Billings pushed up to play four quarters in his second game against the Bombers and was crucial in the 16-point win, finishing with 19 possessions, five inside 50s and two goals.
Montagna has taken on a direct role teaching the 18-year-old and said it was rewarding to see him have such an impact at AFL level after being selected with pick No.3 at the 2013 NAB AFL Draft.
"It was really exciting to see a bit of a glimpse of what he'll be able to produce on a regular basis," Montagna said in Wellington on Wednesday morning.
"He's one guy that I've spent a bit of time with behind the scenes and I was really proud to see him so excited when he kicked that goal in the last quarter.
"You can always see the talent with these young guys pre-season but I probably didn't expect the strong performances they've produced so far so early.
"We know Jack has got the talent but we probably thought he would take a bit of time to really build and he probably still will."
The form of St Kilda's draftees - including NAB AFL Rising Star fancy Luke Dunstan and elevated rookie Eli Templeton - has been key to the club's 3-2 start to the year.
But the Saints have also been led superbly by their veterans, with Nick Riewoldt, Lenny Hayes and Montagna continuing their fine form against the Bombers and filling the top three spots in the AFLCA votes for that match.
"We're just focusing on trying to lead by example for the younger kids," Montagna said.
"It's all just based around our effort and how we want to play.
"If we're going to talk to them about what it takes to play AFL football and play consistently well, we need to be setting the tone.
"We're just making sure we set a strong foundation for the other guys."
He said shedding the underdog tag this week would be a new challenge for the team.
"We probably haven't gone into a game as strong favourites yet this year," he said.
"But the results are irrelevant. It's about how we want to play ... nothing will change whether we're favourites or underdogs.
"(Beating Essendon) certainly does add strong self-belief.
"We're not just a team that can only beat teams around us or lower sides on the ladder.
"So that was really positive that it will give the guys confidence ... that we know we can compete with the good sides."
Twitter: @AFL_Nathan
