From reading, it seems like his rehab was accelerated
by Kayo (2017-04-08 18:36:11)

In reply to: Injuries  posted by AquinasDomer

...which is my way of speculating that he might not have gotten himself back to full strength before playing. The determination to work hard and play ahead of schedule speaks well of the young man; but a sit-out year is an opportunity to revisit rehab, possibly with limits on what he does in practice and how often he practices. That's what Burns did during his redshirt season.

It also is an opportunity to add 20 pounds as you noted.