Contract negotiations are often a search for leverage, and today the Bears bought more than just the running services of Michael Bush for the next four years.

They bought leverage. Lots of it.

Bush was signed to a four-year deal worth $14 million, with $7 million guaranteed, according to ESPN’s Adam Schefter. At 27, Bush would typically be flirting with the elderly running back label, with the inevitable decline anticipated around the age of 30. But much like Fred Jackson in Buffalo, Bush has spent much of his career in Oakland as a backup, and has avoided having to sustain consistent pounding. With Darren McFadden missing nine games, the 2011 season was the first year Bush finished with more than 200 carries.

So even if his birth certificate says he’s approaching the running back cliff, his mind and body disagree, and he averaged 83.9 yards per game during his 10 starts while filling in for McFadden. For the Bears then Bush becomes an investment who could potentially lower their commitment to Matt Forte, or at least force him into training camp sooner and avoid a lengthy holdout.

Forte was disgruntled and annoyed with his contract, but he still had 1,487 all-purpose yards in just 12 games before his season ended early with an MCL sprain. He wants to get paid, and deserves to get paid, but that lack of running back longevity is holding back his payday, and making the Bears hesitant.

Forte will turn 27 next December, and his own recent injury combined with the woefully average numbers posted by 28-year-old DeAngelo Williams after he was given a five-year contract worth $43 million with $21 million guaranteed have advanced the leery feelings towards long-term RB commitments.

New general manager Phil Emery said he used the franchise tag on Forte to buy time, and he has no intention of being wildly frugal and making him play under the one-year tender of $7.7 million. Forte simply wouldn’t play under that contract, because the health risk is too great, and his value is too high.

Coupled with Jay Cutler’s injury, Forte’s absence over the final four games of 2011 was crippling, with Chicago losing three of those games, and fading from playoff contention. Seeing that tumble likely also motivated Emery, as the combination of Marion Barber and Kahlil Bell behind Forte wasn’t nearly sufficient to support a backup quarterback.

That’s the company line that will be pushed. Bush is a backup, and a very effective one who’s proven he can step in seamlessly when the starter goes down. Truthfully, leverage was the primary purchase today.