Templeton, 18, is a strong chance to be elevated to the senior list in the coming week for ruckman Lewis Pierce, who is battling stress fractures in his back.
With Lenny Hayes and Leigh Montagna to miss the clash with the Demons through suspension and reigning best and fairest winner Jack Steven out with a foot injury, the Saints are light on for midfield options.
At Thursday night's season launch at St Kilda's National Theatre, coach Alan Richardson acknowledged the Saints would likely enter the match as underdogs but backed his young engine room to step up.
"In many ways, I think this game is going to typify the spirit in which we're going to play," Richardson said.
"We're going to be a little bit underdone certainly in terms of experience in the midfield.
"We'd much rather have Jack Steven out there, Leigh Montagna, Lenny Hayes, absolutely, but there'll be a group of blokes that go out and play.
"In terms of talent v talent and the way that the media will describe the pre-game, they'll certainly call us underdogs particularly in that part of the ground.
"Our guys will get that done so anyone who plays the role on that particular day in the midfield, we'll be really confident and trust they'll get that done, and that will be typical in the way that we play and the way we judge our performance all year."
Templeton, who won over Saints' fans in the pre-season with his ability to find the goals and his long, blond dreadlocks.
Against the Western Bulldogs in the first of the Saints' NAB Challenge games, the Tasmanian midfielder kicked two impressive goals in extremely wet conditions.
The Saints have been open in their surprise Templeton was still available after the national draft as they would have likely selected him had they held another pick after their three in the top 20.
Templeton will likely edge out small forward Darren Minchington and former Gold Coast midfielder Maverick Weller for the elevation, based on the side's immediate requirements.
Weller is also suspended for round one for striking Greater Western Sydney's Tomas Bugg in the NAB Challenge.
Draftee Luke Dunstan is expected to make his AFL debut against the Demons after an impressive pre-season.
Last year's No.3 overall selection, Jack Billings is also being considered but is less likely to play, with the Saints to take a longer-term approach to the talented midfielder who has had a slightly interrupted pre-season.
Defender Sam Fisher will likely be named despite missing all of the Saints' pre-season games with hamstring soreness.
Shane Savage is expected to make his club debut while defender Luke Delaney remains a chance, but other new recruits Billy Longer and Josh Bruce may have to wait a little longer.
Veteran forward Adam Schneider missed the season launch with back soreness after copping a knock against Port Adelaide on Saturday but is expected to be available.
Steven attended the function on crutches but was putting weight through his foot. In a good sign, he was not wearing a moon boot or cast.
Meanwhile, Daniel Markworth will play his second VFL practice match this weekend after his 2012 knee reconstruction and recent minor setback.
The Demons have already ruled out talls Mitch Clark and Mark Jamar for next weekend, with Chris Dawes unlikely to play and Jesse Hogan rated an outside chance.
Twitter: @AFL_JenPhelan
