In a not-too-distant second place, though, is his competitive nature.
His bio from the University of Florida notes the typical kinds of things - success in high school, including a Florida State 5A championship at Lakeland High, with with the Brothers Pouncey, and being a part of a 4x100 relay team that placed third at the national championships in 2008.
It also notes he defeated two known speed demons - former West Virginia running back Noel Devine, and Florida teammate Jeff Demps, who's an Olympic level 100 meter runner.
Only the supremely confident would challenge such individuals, and only the ultimately competitive would note his victories on his team's biography. And he's not done there, either. He's already challenged, more or less, the reigning Steelers king of speed.
Steelers new RB/KR Chris Rainey says he's got "4.1 speed." Asked if he's fastest guy on team, "Mike Wallace, he's pretty fast ... I'm faster— Will Graves (@WillGravesAP) April 28, 2012
You gotta love his moxie.
That speed and confidence will serve him well, as new offensive coordinator Todd Haley will likely draw up a role of variety for his rookie. He'll likely be seen as a running back and a receiver with the Steelers, as well as a kick and punt returner.
Just getting the ball in his hands will give the Steelers' offense a dimension they haven't seen in quite a while. To get to that point, he'll have to show he's prepared to stand in and block in the famous Backs on 'Backers drill in training camp, the same drill 2010 7th round pick Baron Batch made his name in last year, before tearing his ACL.
That may be an advantage to Batch, whether it's technique, strength or just the willingness to stand in and hit back. But Rainey has the edge in terms of playmaking ability. With a running back depth chart that only has one name written in pen for the 2012 season - Isaac Redman - Rainey has a great opportunity in Pittsburgh to earn playing time.
Assuming he's not busy challenging anyone else to a race.