It's still a bad trade. The whole idea was that they felt they had to trade Hopkins because they couldn't afford to sign him. That's fine. But even if the market was as small as Bill O'Brien is trying to suggest, what are the chances somebody wouldn't have given them at least a 2nd-round pick? Look at the backs drafted in the 2nd round in the past 5 years: Miles Sanders, Nick Chubb, Kerryon Johnson, Ronald Jones, Derrius Guice, Joe Mixon, Dalvin Cook, Derrick Henry, T.J. Yeldon, Ameer Abdullah. It's obviously not a 100% hit rate, but there are a lot of very good backs in that group. If the whole problem is cap space - which makes sense with what they had to pay Watson - then wouldn't you rather have an early draft pick to go after a guy on a rookie contract?
And by the way - David Johnson looked good the first 4 or 5 games of last year. Like really good. Then he got hurt and stopped hitting the hole with authority. It's hard to say how much of that was mental and how much was physical, but if you have a back whose only going to have the confidence to run really hard when he's 100% healthy you're in trouble. How many RBs are 100% healthy for 16 games a year?