One Cover for Nostradamus?

I was looking on the Something Rotten! playbill vault page, and noticed that they only have David Hibbard as a cover for Nostradamus (Brad Oscar), as well as a few other roles. I checked my playbill and it said only his name as well under understudies. Anyone have any more information? If this is true, it seems odd to me that Nostradamus has only one cover, as every other role in the show has two, from Shylock to Shakespere

http://www.playbillvault.com/Show/Detail/Cast/14096/Something-Rotten-at-St-James-Theatre

I could be wrong, but I thought most shows have at least 2 covers for every role. In some interview, I read that you always want to have at least 3 people who can play a role (the actor who goes on everynight, and 2 covers, whether standbys or understudies).

Updated On: 5/26/15 at 01:34 AM

Interesting. Any particular reason the second cover would decline to be in the playbil? I'd think they'd want to be...