It's a great signing because Bush is so versatile. Yes, when he came into the league, he struggled to find his game, but in each year he got a little better and showed a little more of what he can do.
He caught the ball well in New Orleans and was deadly in space. He also returned punts and kicks there. Bush showed he could run between the tackles in Miami with two very productive seasons in a row.
Now he brings that to Detroit, a place where all of his skills can get a ton of use.
While he won't be carrying the ball 25-30 times a game, he'll be asked to run the ball quite a bit. Bush himself said in the press conference that he was excited to see the room he can have with so much defensive attention focused on Calvin Johnson. He called facing just six and seven men in a box "a running back's dream" (per ESPN.com):
The first thing we talked about, we're watching film, seeing those safeties deep ... it's a running back's dream. We have to be able to run the ball in that situation. That's part of the reason I wanted to come here and be part of a balanced attack and take the pressure off Calvin Johnson and Matthew Stafford.
Now, certainly teams will account for Bush in their game plans, but that just means less focus on Calvin Johnson.
You remember Johnson, the guy who was the only weapon in the passing offense last season and still broke records?
It's going to be a nasty bit of pick your poison for defenses.
That's not all Bush will be doing, though, because he'll be catching the ball as well. Whether it is out of the backfield on a small screen or actually running a short route, Bush can catch the ball. Once he has it in his hands, in space?
Getting the ball to him in space will make it even harder for teams to keep an eye on both Bush and Johnson. That's not even accounting for splitting him out as a receiver on a traditional route, which they will likely also do (especially given the dearth of wide receivers on the roster).
Again, it's about getting Bush the ball in space, which in turn will pull attention away from Johnson and free him up a bit.
Given that the Lions threw to their running backs the fourth-most times in the league (144 times, behind Oakland at 145, San Diego at 155 and New Orleans at 178), we know Stafford will be looking for Bush often.
Of course, in a pinch, Bush can return punts and kicks. It's unlikely that he'll do much of that, but considering how disastrous the return units were at times in 2012, let's not take it off the table.
Now, it can be easy to oversell a signing in the first flush after the ink dries. This isn't winning the Lions a Super Bowl, but then again, that's not happening in March and we know that.
There are still issues on the defensive and offensive sides of the ball.
However, running the ball has been an issue for the Lions, and Bush looks like a piece who can put that to rest.