Well, Cozart is a below .300 OBP guy who gets 600 PAs in a season. Mesoraco is a below .300 OBP guy who will probably get over 400 PAs next season.
I'd suggest that while they may have "upside" they are a lot more cause for concern than a bench player who seldom plays and got about 160 PAs last season with a .317 OBP, even if he doesn't hit for power.