Is this a good trade?

Eh, while Johnson isn't a very good running back option. Ward isn't that much of an improvement. Look to pick up Mike Bell (NO backup RB for Pierre Thomas) he's got a great matchup against the Lions and had a very good preseason. That'll give you a little more time to try to organize some good trades. But if you don't want to go with that option, I guess you could go with the trade. It wouldn't be a very good one for you, but you do need another RB badly.