I was instantly reminded of Tommy Hearns when he was getting off the canvas against Marvin Hagler, Sugar Ray Leonard and Iran Barkley.
I'm not buying the back injury stuff. Far more often than not that type of reaction would be related to a head injury, especially since there were multiple periods of abnormality, they all looked the same, he never reached for his back or anything related, and every one of the variables suggested head injury including the oft replayed head thump.
Yeah, I know...outliers. The ever popular outliers. Meanwhile if this had happened to a quarterback on another team I guarantee some of the ones scrambling for the outlier rationale would be matter of factly assessing it had to be related to a head injury. I learned long ago that fanaticism attaches and overrides regardless of topic or occupation.
There is a long history of back problems within my family, including myself and often related to sciatica, which is not always concentrated in the back but rather runs from the butt down the leg to the foot. Regardless, when it shows up the default is to reach for the back.
There's just too much of a parlay component to believe that wasn't related to a head injury. It wasn't one aspect alone suggesting head related. They all trend that way...what he did and what he didn't do. That's a multiplier effect and essentially a parlay, meaning it's an even greater burden to dismiss as a low percentage outlier.
As others have emphasized it can be head related but not a concussion to the point he wouldn't pass protocol. When I was a USC student that program was very early to test for concussions on the sideline during games because there had already been issues with Charles White and others. I remember lots of guys being cleared then sent back out. They probably were too lenient in those days, based on what happened to Charles White later in life.