MLive will chew over each of the Detroit Lions' positions heading into the start of training camp July 30. Today we hit on the running backs.

Running back

Roster locks: Ameer Abdullah, Theo Riddick

Competing: Zach Zenner, Dwayne Washington, Matt Asiata, Mike James, Tion Green

Notable departures: FB Michael Burton

Breakdown: Whether it was by design or circumstance, the outcome is clear. The Lions are going all-in on Ameer Abdullah. And it's easy to see why. He looked excellent in the first two games of last season, averaging 5.6 yards a pop. The Lions cracked 100 yards rushing in both those games.

Without Abdullah in the final 14 games, they did it just once.

He was the only consistent rushing threat Detroit had all season, and then the club declined to sign anybody at the position in the early days of free agency. They didn't draft anybody at the position at all. They did sign an undrafted free agent, Tion Green, who will compete for a power role in the back end of the rotation. And then they signed Matt Asiata, who will be in that same competition. But that's it.

So Detroit is betting big on Abdullah -- that he's healthy, after missing almost an entire calendar year to injury, and that he can stay healthy. And that, you know, he can still carry the football well.

Theo Riddick also appears to be getting healthy too, after missing six games last year because of an assortment of injuries. He underwent surgery on both wrists and has not practiced a down this offseason, but he wasn't among the nine players shelved by injury this week either, and is expected to be available for the start of camp. He doesn't match Abdullah's chops on the ground, but remains a dangerous pass-catcher out of the backfield and provides another dimension to the Cooter Ball offense.

Behind Abdullah and Riddick, Zach Zenner and Dwayne Washington are also back. Zenner is a hard runner who offers value on special teams, while Washington has serious upside if he can ever sort out what's going on between the ears. But neither is a roster lock either with two new additions aboard.

Asiata is a veteran, a veteran of the NFC North, and a physical runner who could help replace the departed Michael Burton. Green is a hard hitter as well, and could be a force on special teams, though it's hard to say exactly where the rookie stands until the pads go on.

Roster projection: Ameer Abdullah, Theo Riddick, Zach Zenner, Dwayne Washington

Other training camp position previews: Quarterbacks, receivers and tight ends, offensive line, defensive line, linebackers, defensive backs