Doesn't make a ton of sense to me, assuming Mancini is actually ready to go.
Mancini/Santander/Mountcastle/Stewart would seemingly be penciled in for 1B/LF/RF/DH with Diaz on deck by mid-season.
Puig may well be an improvement on Stewart or even Santander/Mancini, but this is hardly the season to be focusing on marginal win improvements at the cost of short-term free agent signings.
Maybe a L/R platoon situation with Stewart plus filling in for Mancini once or twice a week and Santander and Mountcastle whenever they need a day off. I assume Mancini won't be playing 155 games.
Puig is only 30 (in two weeks), but I'm not sure how he could get a multi-year deal now considering he couldn't get one last off-season.
Apparently the Orioles are still kicking the tires on Puig as a free agent, according to several articles.
I don't see it myself. But it's being reported.