I don't think the Cardinal's really think that Tavares is a centerfielder. I think they have him projected as more of a RF. I think the trade shows that. An outfield of Holliday, Tavaras, and Craig (Adams at first in this scenario) sounds great offensively, but would be god awful defensively.
I just don't see how you can keep Craig and Adams on the field together long term....unless the cardinals are going to put Craig at Third base, Adam's at First base, Carpenter at second. Or if Tavares is a bust and Craig plays right (not sure how durable Craig would really be in right field long term.)
BTW if you read the Angels message boards regarding the Freese trade they are in full blown meltdown mode. Especially, when the pitching prospect was announced as Salas and not Shelby Miller or one of our top prospects.