If Poirier is an Adams type player as advertised (e.g. rebound, defend, set screens, rim run for lobs) then I think he'll be the one to start at the 5.
Hayward
Thinking he's not going to start this season is laughable. Debating that he won't be speaks to a personal bias and fails to realize that post all-star break the guy shot 55% from the field. His monthly numbers from February forward:
Feb March Apr
PPG 11.9 11.8 18.3
RPG 4.0 4.1 5.3
MPG 26.5 23.8 31.2
FG% 51.3 55.6 65.0
3PT% 44.4 32.0 40.0
His PPG and RPG in March were greatly impacted by the 68 seconds he played in the game he injured his neck on a back-screen. That said, as you see his production increased considerably as the season wore on. So to think he won't be even better 6 months later, and after yet another off-season removed from injury is indeed laughable.
Kanter
He's a good scorer and it's that scoring punch that should be coming off-the-bench. He'll provide instant offense, versus second team bigs, but most importantly will be protected defensively. Teams often target him in PNR's and in space, so it'll be a lot better to maximize his minutes/protect him defensively by playing him against second team guards and mirroring a lot of his minutes alongside Smart. I think Smart's ability to defend, switch, fight through screens will help him tremendously. In addition, I'm pretty worried about a Kanter/Kemba duo defending opposing teams starters in PNRs.
What I think we'll see
Starters - Hayward, Tatum, Poirier, Walker, Brown
Smart for Hayward early sub (say 6 minute mark). Hayward returns at the beginning of the 2Q, or shortly thereafter, and with Walker on the bench he assumes the primary playmaker with the second unit.
This may also be a good time to get Edwards some minutes. He can be the Eddie House to Hayward's Pierce in terms of playing off-the-ball on offense, but guard opposing 1's defensively.