Best Case Scenario:
Line 1: Pavel Buchnevich, Robert Thomas, Jordan Kyrou
Line 2: Zach Bolduc, Brayden Schenn, Jake Neighbours
Line 3: Brandon Saad, Alexandre Texier, Dalibor Dvorsky
Line 4: Alexey Toropchenko, Oskar Sundqvist, Mathieu Joseph
The beauty of this potential lineup is the big upside. You have a lot of talent and there's a good mix of veterans that can ease the rookies into things.
To make this lineup work, you need the top line to be cohesive and play to their potential. Blues fans have been waiting on a top-tier combination for years and they need Thomas and Kyrou to get on the same page.
Buchnevich has had flashes where he has played well with either Thomas or Kyrou, but it's been hit or miss as a trio. The team needs them to be a top line they can depend on.
For the second line, we saw a brief glimpse of what Bolduc was capable of. He had five goals and nine points in 25 games. The points per game isn't a huge positive, but five goals in a short span was a good.
Schenn is better suited as a winger or third liner at this point in his career, but the Blues will need him to still be a second-line center right now. He still has the talent and veteran presence to guide Bolduc. Neighbours has already shown poise beyond his years and an ability to be dependable.
Ideally, I would like a more veteran center for Dvorsky to learn under. However, at least to start, I wouldn't want two rookies on the second line, so Dvorsky has to be on the third line. The upside of this is that if Dvorsky makes the team, it's because he has earned it. Maybe the Blues are a borderline playoff team, but there is still enough NHL-ready talent to make him earn his spot.
Last, but not least, the fourth line. It feels weird to keep Radek Faksa out, but he would be the healthy scratch and first guy in if anyone gets hurt or needs a break.
Sundqvist is more than dependable in this role and you know what you're going to get. Joseph has a slightly higher upside offensively than Faksa and is younger and Toropchenko has the skill to be a third-line player, but would be a welcome addition to the fourth line if the rookies don't pan out.
As an additional bonus, if Zach Dean has a great training camp, the Blues could potentially keep him on the roster and maybe put Faksa or Kasperi Kapanen on waivers. Trading future considerations makes that possible.