The Lions desperately wanted Reggie Bush, and you understand why. He lines up at running back. He lines up in the slot. He goes in motion and every set of eyes that follows him is a set that, theoretically, won’t follow Calvin Johnson.

It makes sense, it really does. Bush has become a vital part of the offense before even playing a down, and if theory transfers to reality, the Lions could be back to busting big plays. But “theory” can be a dirty word around here, and there’s some risk in banking on the veteran Bush, just as there was risk in banking on undersized Jahvid Best.

The Lions have the quarterback and superstar receiver to make this work, but the truth is, it’s mostly on Bush. And he sounds like he’s eager to prove he’s more than some think he is.

“I just want to be a complete back, and I definitely want to show I can be an every-down back,” Bush said Wednesday. “That was one thing I wanted to prove to myself and to people, that I can do it all and wasn’t just a utility back, so to speak.”

The Lions afforded him the best opportunity. While they rebuild their offensive line and retool their defense, they again need a speedy game-breaker to counter their weaknesses. They’re looking for their own Bush Push, for the piece that’s been missing since Best was sidelined, probably for good, with concussions.

Bush, 28, was the No. 1 free-agent target for the Lions, and it’s important to recognize why. It’s not that Johnson and Matthew Stafford required more help than the defense. It’s that in Motown terms, if you spend big money on a fast car, you don’t run it with a clogged fuel pump.

When Bush planted his feet and slightly twisted an ankle during minicamp Wednesday, there were a few nervous Lions, although he was fine. Offensive coordinator Scott Linehan hopes he has an answer for the Calvin Antidote so many defenses employ. Last season, Johnson got his yards (1,964) but not his touchdowns (five), and with defenders sitting back and blanketing him, virtually no one else broke big plays.