2015-2017 defenses were all significantly better than 2018. 2016 was arguably the best defense of the Saban era and 2017 wasn't far behind when healthy. The gap between 2015 and 2018 is significant. What Watson did in 2015 and 2016 is more impressive. Also I find it hard to praise Lawrence for an ability to check it down when most of his yardage came on 3rd and long bombs where the secondary didn't cover or got completely whooped.