I'd pass on a center. Just start Brogdon bring Al off the bench as the backup center. Also want to use Gallo as a stretch 5 because he lacks quickness to keep up with modern 4s on defense let alone do switching. Gallo needs to be in drop coverage. He does still have some advantages vs 5s on offense so he makes more sense playing minutes there.
Brogdon/PP
Smart/ White
Brown/Hauser?
Tatum/GW
TL/Al/Gallo
Bold is top 9 rotation
Why would we change our starting line up from the one that made the finals last season? I don't see it. I see Brogdon off the bench, easier to manage his minutes that way. I see it as more likely that Gallinari starts over Horford than Brogdon starts over Horford.
Least of the team's worries though at this point.
As to Center (or more generally big), we are talking min contracts so no big difference. I actually can't see us going old (Cousins, Howard). More likely take a change to resurrect Bryant or Whiteside.
Reasons
-Al is 36.
-It solves the depth concern at center.
-Reduce turnover woes of starters.
-Reduce the lack of focus/intensity of starters.
-Improve getting to the free throw line for all the starters.
-Gives more open looks for Jays.
-Takes pressure off Smart.
-Puts Al in less ISO.
-Puts your best 5 players out there to start the game.
-Improves game management.
-Keeps Brogdon in the role that made him a steal of a trade.