Camp battles: Who will emerge as the Lions' No. 4 offensive tackle?

Depending on the health of LaAdrian Waddle, this particular position battle could actually be for the No. 3 spot at offensive tackle. If Waddle opens the regular season on the PUP list, everybody behind him on the depth chart will move up a spot, and there will be room for an extra offensive tackle on the 53-man roster, at least for the first part of the season.

If Waddle does not open the season on the PUP list, the battle for the No. 4 spot at offensive tackle will also likely be a battle for the final roster spot at this position. The Detroit Lions already have an established top three of Riley Reiff, Waddle and Cornelius Lucas, so if all of those guys are on the active roster, chances are there's only room for one more tackle.

The candidates

This camp battle is so interesting because of the backgrounds of the three players in the mix for the fourth spot at offensive tackle. Corey Robinson, for example, is a rookie after being picked by the Lions in the seventh round this year, and he switched positions multiple times while at South Carolina, going from the offensive line to defensive tackle and back again.

Similarly, Xavier Proctor, one of the other players in this position battle, just recently switched from defensive to offensive tackle. It's much tougher to make that switch when you've already been in the NFL for a couple of seasons, but he's looking to jumpstart his career on the offensive side of the ball.

Continuing the theme of changing positions, Michael Williams is now in his second year at offensive tackle after originally joining the Lions as a tight end. He was known best for his blocking abilities coming out of college, so his position switch last year didn't come as a huge surprise. He actually looked pretty good in the preseason last summer, and he spent the 2014 regular season on the practice squad.

Who has the edge right now?

Given that he only recently switched to offensive tackle, Proctor is a long shot at best, but it's a tough call between Robinson and Williams. On the one hand, Robinson was just picked in this year's draft, and he was a three-year starter at South Carolina. On the other hand, Williams has more NFL experience, although he's still relatively new to the offensive tackle position by comparison.

It's really a coin flip right now, but I'm going to give Williams a slight edge for the No. 4 spot at this point, if only because the Lions have been developing him as an OT for more than a year now. Of course, that won't mean anything if Robinson clearly outperforms him in training camp, and perhaps the Lions will value Robinson's upside instead. For now, though, if the season started today, I'd have to imagine the Lions would feel more comfortable with Williams in the two-deep.

Previously: Backup quarterback, starting running back, No. 4 running back, starting fullback, No. 3 wide receiver