THone .. good color photo of the drumhead  http://t.co/qMQgFTDW 
twitter backtracks to the other BotS opener, Jake Owen
https://twitter.com/jakeowen 

WDMJ .. not sure where you're getting your info .. every show/region will be different I'm sure, but Jake plays first and he seems to have a pretty solid country following that will then hear (probably new-to-them) GPN .. this is from a Target Field show review I hadn't already deleted .... 

<i> More than 40,000 fans packed the downtown Minneapolis baseball stadium Sunday, July 8, . . . .
The music started early, with opening performances from Jake Owen ("Barefoot Blue Jean Night") and Grace Potter and the Nocturnals ("Never Go Back"). Most of the crowd was already inside the gates for Potter's show and firmly settled in by the time McGraw rolled on stage. </i> 

http://www.twincities.com/ci_21033963/review-kenny-chesney-tim-mcgraw-at-target-field