I think the reason that some want to believe that Vaughn is "ready" is that EE has struggled this far.
If EE cannot fulfill the Sox expectations this season, they conceivably could bring up Vaughn.
Mazara is obviously the other player in the line-up that has been a disappointment. No home runs for a guy that big and strong ? We are all waiting to see a 500 foot bomb and instead we get way too many K's from Mazara in clutch situations.
This is a shortened season, so perhaps the Sox should respond to under-performance with more urgency and make personnel moves that they normally would hold off on.