Manning was also a huge factor in how their defense was constructed. Their defense was built around small and speedy guys to fly around the field, rush the passer and protect leads in shootouts.
The truth is I don't think they were finishing but 8-8 at best with Peyton. They were lucky to get to 10-6 last year. That team has been on a steady decline for a while thanks to bad drafting. Look at their 1st round draft picks ... Tony Ugoh, Duane Brown, Marlin Jackson, Anthony Gonzales, Jerry Hughes. They basically haven't had a decent draft since 2007.