We're a month in now, so I think you can start to judge players with a reasonable amount of data.

I'm not as set against Dow as some others but he's averaging 12.5 disposals across the first month, and statistically speaking, his best game was his first.
Setterfield is averaging 13.7 from three games, although that's skewed slightly by a very quiet game against Collingwood.

Every other player who mostly plays midfield is putting up better numbers in the opening month, so these two are the current 'weak links' in the midfield rotation.

From all reports the next three cabs off the rank for the midfield are Kennedy, Cunningham and Stocker.
Kennedy might make us a little slow in midfield (although against a midfield featuring Wines and Boak that might not be a huge issue).
Cunningham has pace, but doesn't really play full midfield minutes, so he's not a real replacement mid.
Stocker is a big chance.

Across the rest of the ground, you can sort-of point to moments in each game where most of the current best 22 did *something* to justify their spot (although in the case of Casboult the something is being able to ruck, and generally "working hard").

Of replacements or suspects?

However, I don't actually expect us to make four changes to a winning team, assuming JSos is out and Plowman ends up being sore. We rarely make that many changes.

In regards to Silvagni, the obvious options are McDonald, McGovern or going smaller with Cunningham. Given how tall Port play up forward, I'd be tempted by McDonald as a swingman.

If Plowman is out, I'd play McDonald for the same reasons. Port play tall up forward with Dixon, Ladhams / Marshall and Georgiades. We probably need another tall option down back. I'd also think about playing Casboult back on Dixon, but we rarely mix things up like that.