Their secondary is nowhere near as good as Denver's. Josh Norman is good, the rest of their back 4 is average to below. They've been lit up multiple times this season. No QB outside of Big Ben has had a good day against Denver's defense (and Carolina's passing game isn't in the same league as Pittsburgh's). Their front 7 is really salty though, but Thomas Davis' injury will have an impact. Even if he plays, his ability to get off blocks and wrap up will be affected.
Who are you trying to convince?
It doesn't matter if the Panthers' secondary is "nowhere near as good as Denver's (not true, by the way)." The Panthers' secondary is not playing Denver's secondary. They are facing Peyton Manning. This is not the 2013 Peyton Manning, let alone the 2006 Manning. And don't think you are giving Carolina enough credit. Coleman was among the league leaders in interceptions and as a team, Carolina has a +20 turnover ratio, tops in the league. Denver is -4, tied for #19. Denver is facing Cam Newton. Carolina is facing Peyton Manning.
Carolina's passing game is not the same as Pittsburgh's, but Newton and Roethlisberger are not the same type of player either. I don't think Denver has ever seen an offense like Carolina's this year. Alex Smith can scramble, but he is not on the same level as Cam Newton. Not even close. Also, Carolina has beaten the #2 twice (Seattle), #3 (Houston), #5 (Dallas), #7 (Tennessee), and #8 (Arizona) passing defenses in the league.