Football Outsiders Q&A Part 2: How much is Theo Riddick worth?

This is Part 2 of a five-part Q&A session with Football Outsiders’ Assistant Editor, Vincent Verhei. For Part 1, where we talked about Jim Bob Cooter’s impact on the offense, click here.

According to Kyle Meinke of MLive.com, Theo Riddick could be the next Detroit Lions player up for an extension. Riddick’s rookie contract (four years, $2.251 million) expires at the end of the 2016 season.

Riddick was undoubtedly a huge part of the offense in 2015. He was third on the team in both receptions (80) and receiving yards (697). But oddly, Riddick was hardly a part of the team’s rushing game. His 133 rushing yards was good for fourth most, behind even quarterback Matthew Stafford.

With such a unique skillset, we were curious as to how much a guy like Riddick would be worth to this team. So we asked Football Outsider’s Vincent Verhei that exact question. Here’s his amazingly detailed answer:

Q: The Lions are reportedly working on a contract extension with Theo Riddick: What is the value of a running back whose primary function is in the passing game?

A: That's a really good question, and one that sent me on a wild stat hunt. I ended up writing more than 600 words on this, but you can skip to the end if you don't care about the process and just want to see the answer.

In his career, Riddick has gained 1,039 yards receiving and 209 yards rushing. So 84 percent of his total yards from scrimmage have come through the air. That's a very, very unusual split. I checked the top 500 players in yards from scrimmage in NFL history, and here's a full list of players who gained 80 to 90 percent of their yards from scrimmage via the pass:

* Kyle Rote, who started at halfback for the Giants of the early 1950s before moving to receiver by the end of the decade.

* Ray Renfro, who started as a halfback for the 1952 Browns before moving to receiver.

* Preston Carpenter, who was a rookie running back for the 1956 Browns, then spent 12 more NFL seasons primarily as a receiver for five teams.

* Johnny Morris, a returner/receiver type for the 1960s Bears who played a little halfback in his career before moving full-time to receiver.

* Charley Taylor, who spent two seasons as halfback for Washington in the mid-1960s before moving to receiver, where he made the Pro Football Hall of Fame's all-1960s team.

There is an obvious common theme among those players, and it probably tells you where Theo Riddick will be found on the Lions roster starting in 2017.

Even breaking it down into single seasons, it's hard to find too many players in that 80 to 90 percent range, especially with 800-plus yards from scrimmage like Riddick had last year. Twenty-two wide receivers have done it (counting Joey Galloway twice), but only two running backs: Keith Byars with the 1990 Eagles (813 receiving yards, 141 rushing yards) and Amp Lee with the 1997 Rams (825 receiving yards, 104 rushing yards). If we drop that total yardage threshold, we start to find familiar names among receiving backs, guys like Larry Centers and David Meggett and Kevin Turner and Todd McNair. But even most of those guys played in the last century. New England's James White and Oakland's Marcel Reece were both in that range last season, but they had less than 800 total yards between them.

So that's a lot of interesting data on just how strange a player Riddick is, but we're no closer to measuring his value. By our numbers, Riddick is second in receiving value the last two years behind Pittsburgh's Le'Veon Bell, but remember that Bell (and other high-value receiving backs like Matt Forte and Ahmad Bradshaw) add lots of running value too, so just comparing their receiving numbers to Riddick's seems unfair. And we can't do a straight comparison of Riddick's receiving numbers to those of players at other positions, because we use different baselines for running backs than we do for wide receivers, so it's an apples-and-oranges comparison.

So let's try this: Instead of looking at each player's receiving value, we can look at Matt Stafford's passing value when passing to each player. I know that sounds the same, but I promise you, it's not. In this light, we see that Calvin Johnson was by far the Lions' most valuable receiver last year (duh), with Golden Tate second and Riddick edging out Eric Ebron for third. If we use this same methodology for all teams, Riddick finishes 46th among all players, right behind Julian Edelman and James Jones, and right ahead of Zach Miller and Emmanuel Sanders. There's a huge range in the salaries of those four players, but their average actual payout was about $3 million in 2015.

So to summarize all that down to one sentence: Riddick should be thought of as a slot receiver, not a running back, and should be paid accordingly, somewhere around $3 million a year.

Thanks again to Verhei for his answers to our questions. If you want more detailed analysis like this, be sure to grab Football Outsiders’ 2016 almanac for the NFL season.

Tomorrow, Verhei will answer why the Lions’ defense took such a step back in 2015.