I'm not up to date with the medical literature on knee ligament injuries, but Wentz tore his ACL and LCL. I think AP might've skewed perception on how easy it is to recover from ACL injuries. The fastest times for recovery are supposed to be six months, but from what I know, most orthopods recommend closer to nine months. That puts him right up against training camp, so I can see that. The LCL tear has to add another dimension, right?
Shead sustained ACL and meniscus tears and it took him about 11 months to recover. I'm just not sure he'll be ready before week 4. I'm sure he'll prove me wrong, he's a heck of a competitor, but a lot of the healing process is out of his hands.