Their coverage isn't super-deep, even if they've all had a chance to rehearse everything they're covering. Seven swings (plus two understudies who usually play other roles and one who doesn't), Herbie is the only role with two understudies listed, one understudy covers Tulsa, Yonkers, Little Rock and Angie... Shows that have been running have mostly learned not to go into winter without lots of extra coverage, but that'd be difficult for a show that's only just opened.
So maybe not wanting to proceed if Audra can't go on is part of it, but it might not take that many others being out (or just the "right" combination of others) for them not to be able to go on even with her standby. |