Jahvid Best was a terrific player at the University of California and then ran a 4.35 40-yard dash at the NFL combine. There are two main doubts about him at the next level. Best dealt with nagging injuries early on at Cal, but then suffered two concussions during his junior year. The second concussion was particularly gruesome and it cost him the remainder of his college career. But the bigger doubts Best must overcome relate to his size; at 5'11, 199, some question whether he can be an elite fantasy player. Why is that? Over the past three seasons, only three sub-200 running backs have finished in the top 24: Chris Johnson, Jerome Harrison and Steve Slaton. Slaton looks like a one-year wonder and Harrison may end up being a one-month wonder; that leaves Chris Johnson and not much else when it comes to recent fantasy value by smaller backs. So are Best backers being duped by visions of Chris Johnson dancing in their head when the odds are that most backs his size won't make it?

Let's start by defining what "his size" actually means. It's a more complicated question that I initially thought. Maurice Jones-Drew is "only" 208 pounds but he packs that on a 5'7 frame; he has a BMI of 32.6, much "bigger" than that of the average running back. (BMI is a measure of size calculated by comparing a person's height and weight.) Darren McFadden is heavier than MJD, but at 6'2, 210, his BMI of 27.0 means he has a much lighter, leaner frame than Jones-Drew. On the other hand, there's something to be said for blunt force; a back that weighs 220 pounds can punish a defense much more than a back that weighs 195. In the end, both "weight" and BMI matter.

So how do we compare weight and BMI? There are many ways you could do it. Here's what I did:

1. Recorded the weight and BMI of every running back with at least 100 carries over the past five seasons. I used a cut-off of 100 to make sure that I only included running backs who played on a semi-regular basis at a minimum.
2. Measured the average weight and average BMI of the group, along with the standard deviation of both variables. The average weight was 218.2 pounds, with a standard deviation of 14.9 pounds. The average BMI was 30.4, with a standard deviation of 2.0. This means a running back would be one standard deviation heavier than average if he weighed 233.1 pounds, and he'd be one standard deviation below average if he weighed 203.3 pounds. Assuming a normal distribution, this also means that about 68% of all running backs in today's NFL that carry the ball at least 100 times in a season have a BMI of between 28.4 and 32.4.
3. Assigned each running back a weight and a BMI grade on a scale where 100 was average, and every 15 points correlated to one standard deviation above/below average. Now that the two variables were on the same scale, I averaged the numbers, to assign a "size" grade to each running back.

Full disclaimer: Some of you will think steps two and three look like math gibberish. It mostly is. Unfortunately, a simple question like "which running backs are the biggest" has a complicated answer. While the math and the formula was complicated, the results match what any average football fan would know. Essentially, I'm just objectifying what we see when we watch the games.

But all of the above is just background information. Let's get to the point of the post. I looked at all running backs drafted inside of the first 50 picks (Best was the 30th pick in the 2010 draft) since 2000; I chose to exclude prior years because in earlier eras, running backs (and all players) were smaller. There were 42 such running backs; three of them did not play as rookies due to injury. In looking at the remaining 39 runners, I wanted to see if there was any correlation between size and fantasy value. The table below shows the year each running back was drafted, which draft pick was used on him, his BMI, height and weight as a rookie, and his rookie VBD number. The last three columns show the players scaled weight and BMI (with 85 being one standard deviation below average, 70 two standard deviations below, etc.) and finally, the last column is "size." Size is the average of the scaled weight and BMI categories, and is the variable by which the table is sorted.

As you can see, Best has a size grade of 80. There's no denying the fact that Best is smaller than your average back -- quite a bit smaller, actually. But he was also a high draft pick. And has incredible speed. Sure, you don't see many successful backs as small as Best ... but you don't see many backs as small as Best get drafted in the first round and then bust, either.

And that's the point. Only five of the 39 running backs in the table above had a size grade of 85 or lower; two of them had VBD value as rookies. It's true that in the middle range, from 90 to 110, there have been eight successful rookie running backs. But there were 25 running backs drafted in that group, which means only one in every three were successful. That's pretty similar to the ratio for the tiny backs, too. When looking at Best, I think the right way to analyze him is not as a small back but as an incredibly fast back. And those guys are often successful as rookies, even if they're small. Yes, small backs don't usually make it in the NFL, but Best has already cleared the largest hurdle. By being good enough to be a late first round pick, Best should only be compared to similarly drafted players. And it's not like there's a long list of light-weight, first round running backs who didn't have fantasy value.

As for Best's long-term prospects, I think his size is a non-issue. When Ray Rice went to the NFL combine, he was 5'9, 195, similar to Best. Then he stopped being a student and started being an NFL player, and added 15 pounds of muscle to his frame in two years (he's now listed at 210 pounds). Clinton Portis was 5'11, 205 as a rookie, and dipped well below 200 pounds during his rookie season. Now he's listed at 221 pounds. Once Best bulks up to 5'11, 215, no one is going to question his size. I wouldn't worry about it for 2010, either.

Questions, suggestions and comments are always welcome to [email protected].