Well said. More than likely, there must have been some residual "functional" weakness of his hamstrings after his ACL rehab, which is unusual because in my experience the hamstrings actually get stronger than the contralateral side during the post-op ACL process.
The Vikings handled his injury very poorly, but unfortunately is typical in the NFL; it seems as if hamstring injuries are viewed as a "minor" injury with players being rushed back too soon. Too many times, the player suffers a reinjury and it turns into a season long battle. Hamstrings are too important to athletic function to take lightly. Looking back at Barkley's hamstring injury in the preseason, there was all this concern about how the injury must have been "more severe than was being let on" because the Giants essentially shut him down for several weeks, when the reality is that the medical staff handled it perfectly (at least it seems so far...knock on wood as a Giants fan).
I get it that the NFL season is really short compared to other sports, so missing 4-5 weeks with a hamstring injury in the NFL is a major portion of the season, but the time it takes the body to heal doesn't take that into account, we know (approximately) how long it takes a muscular injury to heal from a physiologic standpoint, and nothing can change that no matter how much we wish for it (or at least stem cell technology becomes perfected).