Bush has previously played for the New Orleans Saints and the Miami Dolphins, but did not begin to impress until he joined the Lions before this season.
"When I look back, I'm so much more advanced in just my vision, my understanding of schemes, linebackers, where they have to play their gaps and just all the different things that come along with being a running back," Bush told ESPN.
"So it's taken a while. It didn't happen overnight. It took me a while, took a couple of years. I would say it took a good four or five years until I really had a true, good understanding of defenses and schemes and how to run the ball."
This is Bush's eighth season as a pro.