The Detroit Lions report to Allen Park, Michigan, at various points this week to start the 2017 season -- rookies early in the week and veterans on July 29 leading up to the first day of practice on July 30. To get you ready for that, we'll give a little bit more insight into each position group as camp gets ready to get going throughout the week.

Now, we'll look at running backs.

Players: Ameer Abdullah, Matt Asiata, Tion Green, Mike James, Theo Riddick, Dwayne Washington, Zach Zenner.

Roster locks: Abdullah, Riddick.

All about the health: Since the Joique Bell-Reggie Bush tandem had extremely strong productivity in 2013, the Lions have struggled to have a completely healthy and viable backfield. Bush was hurt for most of 2014 and was cut after the season. Bell wasn't healthy for most of 2015 and was cut after the season. Abdullah missed almost all of 2016 with a foot injury and the Lions were so beat up here they eventually turned to Justin Forsett (before eventually cutting him) and Bell again. Riddick bounced on and off the injured list throughout most of last season before having surgery on his wrists -- something he's still recovering from. When healthy, this position group has a chance to be good, something seen in a short burst during the first game of last season -- the last full game the Lions had their complete core of Abdullah, Riddick, Zenner and Washington healthy. Injuries will happen here, but the key is Abdullah. If he can remain healthy through the season, he has a chance to be a breakout candidate and show the promise he flashed during his rookie year in 2015. If injuries slow Abdullah and Riddick again, there will be problems.

A role for Zenner: The former South Dakota State running back showed real promise at the end of the season, when he had 67 rushing yards and two touchdowns against Dallas and followed it with 69 yards and a touchdown against Green Bay. It was the best -- and most consistent -- Zenner has looked in his career and though it's a small sample size, it also showed there should be a role for him this fall. He's not a roster lock, although I was close to making that move, simply because he's not going to be a starter and if he doesn't show up well during camp there are multiple players on the roster who can overtake him for a spot. Plus, running back feels like a position where the Lions could end up adding a player during camp if they start to have questions about what they see. But as of now, with this roster construct, Zenner should be able to play his way into the No. 3 spot. Plus, he's a good character guy who has special-teams value as a blocker on kick returns.

Washington is the wild card: His skill set is fascinating, a blend of size, strength and speed that enticed general manager Bob Quinn to use a seventh-round pick on him in the 2016 draft. And the Lions saw enough out of him to keep him on the roster last season and make him the team's early No. 3 back over Zenner. But his vision was questionable too often last season. His pass protection was nowhere near the level of Zenner or Riddick. And he didn't seem like a player the franchise could rely on once injuries set in. Plus, he had injury questions of his own last season, too. If he's able to fix his vision -- something that can happen with diligent film study and repetition -- and improve his pass protection, he's a player who could be a surprise in 2017. If he didn't work on that in the offseason, he might not make the roster. More than any other running back, he's the guy to pay attention to over the next month-plus. Winning a return role, either as a kick or punt returner, would also go a long way toward solidifying his future in Detroit.

Depth is the key: With the Lions essentially eliminating the fullback from the offense by cutting Michael Burton, the potential for a fifth running back on the roster dropped a bit. But if Asiata, Washington, Zenner, James or UDFA Tion Green can shine on special teams and do what Zenner did a couple of years ago, leading the league in rushing in the preseason, that player could force his way onto the roster. As of now, I'd go with Zenner and Washington on the roster and Detroit going with only four backs, but so much can happen over the next month. The number here is going to be four or five, depending on special teams battles and injuries throughout the rest of the roster. But Detroit learned last season how important depth is here.