Quinn has shown he is ready however. He might be our second best outfielder NOW. Saunders is only average defensively. Kendrick is a 700 OPS guy with average defense and little speed these days. Altherr may not hit enough.
There are questions with Quinn in terms of durability, but not really talent. And I agree with the poster a few days ago who said that durability was not enough of a reason to keep him in the minors. As a reserve OF they would not be counting on him to play every day. His injuries have also been more of the freak nature rather than chronic. At some point if he shows he is better than everyone else the team needs to play him. He is healthy now as well.
He also is already on the 40-man so we end up losing one less player by him making the team. We will have more 40-man flexibility in a month or two with injuries also.
As I said, they probably won't do it. But that does not mean they should not do it. Quinn is better than Stassi or Coghlan. He adds something that the team lacks. They can find him enough playing time too, especially if they use double switches aggressively. If any slower player gets on base starting in the 6th inning (this includes Kendrick, Saunders, Joseph, Franco, and whomever is catching) you can double switch Quinn in a little early. That potentially is a huge weapon that also lets Quinn play 3 innings on average in most games when he is not starting.