Diagnosis for Ho-Pin was mild concussion. He is not cleared to qualify. Looks like Dragon racing has called up Patrick Carpentier as a backup driver. If Carpentier could get the car in the field, Ho-Pin could still race next week (it is the car that qualifies for the race - more or less - there's a lot to it). [instant update] There may be more to it, as Carpentier was practicing Scott Speed's car and wrecked it in the morning bump day practice. Stay tuned.
4 of the 5 Andretti cars failed to qualify day 1 and will have to fight their way in. The only one that made it was the yearly one-off collaboration with Petty for John to drive the #43. I can only think that the team tried something that didn't work out for them.
One other possibility not on the Autosport list is the second Sarah Fisher Racing car, which she said she might put in line if the primary car qualified well, which it did. Could be used by a driver who's car isn't quite up to par, or by someone yet unknown.