If Pep is considering Busquets as a starter (which he probably do) - Mascherano doesn't make sense then, because he's not a player who could be a part of a rotation policy. Maybe someone like Martinez would be a better option.
If Pep doesn't consider Busi as a starter (which I highly doubt), then he's the best we could get right now, taking into account the fact that he didn't sign his new contract yet, which means an easier exit from his current club.
But if we're really going to get Cesc, I'm not sure what our iconomic situation is atm.