It's so easy to overlook just how long rookies are playing.

They finish up the college season, some of which have 1-2 playoff games ontop of the regular season. Then they start training for maybe the senior bowl or shrine bowl. Then they start training for the combine which is football but not really football. Then they start training for pro days which is football but it's a lot of stuff that never impacts football. Then it's the draft. Then it's rookie orientation and getting up to speed with the NFL lifestyle. Then it's offseason training, OTAs, etc. Then it's the preseason and then the regular season.

The first offseason an NFL rookie gets is the first real break these young men get is probably over a year. So that second year jump can be so big simply because the players haven't had a chance to take time off.