The doubt that arises with a player like Bush is one of the more obvious detractions to any fantasy back: injuries. He's had calf, hamstring and right leg injuries that have cost him 21 games over his career. These concerns have robbed the former No.2 overall pick the chance to achieve the "feature back" status that most top-ranked NFL running backs are afforded.
The other knock against Bush is that he doesn't produce yards between the tackles like the most productive backs in the NFL.
Yet it's worth noting that in his two seasons with the Miami Dolphins, Bush missed just one game. He averaged a healthy 5.0 and 4.3 yards a carry in those seasons on 216 and 227 carries, respectively. While with the New Orleans Saints (2006-2010), Bush never eclipsed 157 carries in a season. In Miami, he showed a willingness to run more between the tackles and proved that he wasn't just a glorified pass-catcher, which was sometimes the knock on him in New Orleans.
Now he's with the Detroit Lions. No, they didn't have a terribly great running game last season. The Lions ranked 23rd in rushing because they played most of their snaps out of the shotgun formation and had the most pass-happy attack in the league.
But the signs for Bush to have a productive season in Detroit are there.
Jim Schwartz has stated that Bush could catch as many as "60-80 passes" next season, which would be a significant upgrade over his two seasons in Miami, when he caught a combined 78 passes. And before you say that's just "coach speak," consider that Detroit's backs last season caught 96 passes for 778 yards.
Let's stay conservative and say Bush grabs 60 passes. And we'll say that he's in a timeshare with Mikel Leshoure and they more or less split the number of snaps and number of carries.
Even still, that 60-reception number is ridiculously conservative, given that the Lions were relying on the likes of RBs Joique Bell, Leshoure and Kevin Smith to catch passes. Dig as deep as you want, you won't find half of Bush's playmaking and pass-catching talent in all three of those guys combined.
Even the rushing split I proposed is questionable, given that the only other candidate for early-down work is Leshoure, whose 215 carries yielded an ugly, indecisive and plodding 3.7 yards per carry.
Given that workload—and assuming Detroit runs a relatively similar offense to what they did last year, which they probably will have to given their personnel—Bush can expect around 195 carries and 60 catches.
Most of the running back catches in Detroit come off of delayed screens, which are ubiquitous in today's NFL because they offer shifty backs the opportunity to make plays in space. Bell's 52 catches were able to yield an average yard per catch of 9.3. One of Bush's predecessors, the similarly talented playmaker Jahvid Best averaged a combined 9.1 yards per catch in his two seasons with Detroit.
Extrapolating that to 60 catches, we have a yardage production of at least 540-600 yards. If Bush is even average running the ball, 195 carries at 4.0 yards a carry produces 780 yards. In total, we're looking at a minimum of 1,400 total yards (excluding any punt or kickoff returns).
Bush had four seasons where he exceeded 200 touches, and he scored eight, six, seven and eight touchdowns in those seasons.
A 1,400-yard season with eight touchdowns is 186 fantasy points in any standard league, and in 2012 would have ranked him No.13 among running backs in scoring, placing him in the same league as Trent Richardson, Frank Gore, Stevan Ridley and Matt Forte.
As we have established, those numbers are conservative estimates and have in no way accounted for the fact that Bush is much better at football than any back Detroit has employed in the Matthew Stafford-Calvin Johnson era.
His worst-case scenario places him just outside the top 10 for fantasy backs, and any small improvement above and beyond that standard easily pushes him into that top-10 territory. In fact, he becomes at that point a borderline No.1 fantasy back in a standard-sized league.
And yes, you can pick him up in the fourth round because of an injury history that he seems to have put behind him. Draft Reggie Bush as a No.2 back in 2013, and watch him outperform your No.1 more often than not on a week-to-week basis.