The Saints suffered a 33-point loss to Brisbane on Saturday afternoon at Marvel Stadium.
Wanganeen-Milera fought through close attention from Jarrod Berry for a half, before the Lions dropped the hard tag and took control of the midfield battle late.
The 23-year-old finished with 29 disposals, 698 metres gained, five clearances and 10 score involvements.
But the Lions surged in the final quarter when Wanganeen-Milera spent time off the ground, with Will Ashcroft dominant and the likes of Darcy Wilmot, Berry and Levi Ashcroft also influential.
"I thought he looked good, but he's got a lot of improvement (to come), and as he gets more support around him and we build out more quality, he will get better and better," Lyon said.
"I'm actually talking about the growth of other players to his level.
"You've got to rise. Watch the gap. The Ashcrofts have risen to the level of Hugh McCluggage and Lachie Neale, haven't they?
"We've got a few that need to rise with Nas."
Lyon wouldn't buy into how big an impact losing Cooper Sharman (three goals) to concussion in the third quarter had on the course of the game.
"We can't live in that space. No alibi, no excuse. We've got to step up," he said.
"So look, we'll take the feedback. We're all a bit disappointed, but in saying that, I think the foundation is strong to try and improve off.
"We get the bye and we'll get a couple back, hopefully over the next few weeks.
"We'll take the feedback, learn, aim to improve and then set ourselves for Port Adelaide.
Expectations were high after the Saints' off-season recruiting spree, where they secured Tom De Koning, Jack Silvagni, Sam Flanders and Liam Ryan.
While Lyon's charges were competitive against Collingwood, Melbourne and Brisbane, they only have a win over GWS to their name this season.
"All I know is that we play that level of footy, we're gonna win more than our fair share of games," Lyon said.
"It took a pretty good team to wrestle back over the top of us, so we take confidence from that."
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