It's been a topic for a while now, this idea of David Johnson getting a contract extension. Now that he has it, the extra years that keep him a Card until at least 2021, it can only help, if for no other reason that it's not a subject.
Johnson emphasized this past week that the contract wasn't the only thing motivating him. It bugs him that some don't seem to remember how great he really was in 2016, with more than 1,200 rushing yards and almost 900 receiving yards and 20 touchdowns. His injury was to his wrist last year, not his legs, and while Johnson's smile may be one of the most genuine and prevalent in the league, you can see when he talks about his ability that he does not love that it might be overlooked (whether many are actually doing that or not.)
But yes, the contract was a thing. That's understandable. Johnson was still on his rookie deal, and he wanted to set himself and his young family up for life, and in a league where you never know how long your shelf life might be (especially as a running back) that's just real life. Do I think Johnson was going to play differently if the contract hadn't gotten done? No. That's not Johnson's style. When he talked about how excited he was to play this week -- before the deal went through -- it sounded honest. Perhaps Johnson knew they were creeping closer to an agreement, but still, a contract is never done until it's done. Johnson is also the kind of guy who struggles not being around team-wise, as witnessed by his offseason when he sat out a little because of the quest for a new contract but never really went all in in that regard.
If the multiple reports on the money are right, Johnson got good guaranteed money ($30 million) that could be great ($45 million total worth) if he plays like he has and he stays healthy. That's all what both sides want now. Johnson was always going to be the linchpin of this offense. Now he is happy he is being paid like it.