I'd guess Siegler has a better shot at sticking as the back up than Darrien does. He couldn't hit in the Southern League and the defense is no where near the level it would need to be for him to get a call up. If you reaaaally want someone from within the org not named Quero it would be either Wood or Rodríguez, and I doubt they would be very successful.
So yeah, I agree with biedergb. A minor trade or an FA. Diaz, McGuire, Thaiss, etc still out there as serviceable backups for early in the season before a Quero call up.