The Lions kick off the OTA portion of their offseason schedule this week, which means they can operate 7-on-7, 9-on-7 and 11-on-11 team drills.

It's the first time the rookies will join the veterans in a practice-like environment, though there is no contact allowed.

The team has scheduled 10 voluntary OTA practices over the next three weeks leading into next month's mandatory three-day minicamp.

Here are five things to watch as the Lions begin OTAs:

1. Who slots in first at left guard?

The rest of the offensive line is set with Taylor Decker at left tackle, Travis Swanson at center, T.J. Lang at right guard and Rick Wagner manning the right tackle spot.

Graham Glasgow, Laken Tomlinson and Joe Dahl are the top three candidates to fill the vacancy at left guard.

Glasgow replaced Tomlinson as the starter midseason last year, and seems to be the favorite to land the gig heading into this season. But head coach Jim Caldwell said earlier this offseason that Tomlinson went right back to work after last season concluded. Caldwell expects him to compete hard and be in the mix.

Then there's Dahl, who needed to be taught some technique things as a rookie after playing tackle in a pass-happy system in college, but general manager Bob Quinn said at the Combine in February that he really liked how Dahl's development was coming along.

Who begins the offseason with the first unit? How do they rotate in? It's something to keep an eye on over the next few weeks.

2. Ameer Abdullah and Theo Riddick health

Detroit's top two running backs were on the field together last season for a grand total of just a game and a half before Abdullah suffered a season-ending foot injury.

Riddick dealt with health issues of his own, most notably wrist injuries that forced his season to end prematurely after just 10 games.

Abdullah spoke to reporters at last week's Taste of the Lions event, and said he was back on the field in late February or early March. It's expected that he participates in OTAs at some level.

Riddick's availability is a little bit more of a question mark. When asked at the league meetings in March about Riddick and his ability to participate in the offseason program, Caldwell was less committal than he was with Abdullah.

"We'll see," he said. "That's one of the things having what he had done, he'll work through it. We'll see where he is once we get going. But one thing's for certain, we'll let the doctor's kind of let us know, lead the way in that regard."

Abdullah rushed for 101 yards on 18 carries last season and caught five passes for 57 yards.

Riddick ran for a career-high 357 yards. He caught 53 passes and had five receiving touchdowns. That after catching 80 balls the year prior.

In the two games Abdullah and Riddick were on the field together, the Lions rushed for more than 100 yards as a team. They reached that benchmark just once the rest of the season without Abdullah.

We'll get our first look this week at the health status of both players.

3. Linebacker lineup

No unit outside of maybe the offensive line underwent as much shakeup as the linebacker position this offseason.

DeAndre Levy and Josh Bynes are no longer with the team. Jarrad Davis, Paul Worrilow, Jalen Reeves-Maybin and Nick Bellore have been added to the mix.

Davis, who the Lions took with the 21st overall pick in this year's draft, is expected to be a Day 1 starter, much like Decker was as a first-round pick last year. Decker slotted into the left tackle spot Day 1 of open OTAs.

Quinn told detroitlions.com after selecting Davis that he expected Davis to play the MIKE, and hoped he'd be calling the defense for many years to come.

So, where does that leave Tahir Whitehead, who started every game he played last year (15) at the MIKE. Does he compete with Davis at the MIKE?

Whitehead does have experience playing the WILL and SAM spots. Could he be moved to one of those?

Reeves-Maybin and Worrilow will also be fighting for playing time, along with second-year player Antwione Williams, who veteran safety Glover Quin said earlier this offseason was a young player to watch this season on defense.

How will all these linebackers be rotated to start OTAs?

4. Cornerback shuffle

Just like the linebacker position, there's a lot of new faces at cornerback too.

The Lions return all three starters from last season in Darius Slay, Nevin Lawson and Quandre Diggs (slot). However, the team also signed veteran DJ Hayden in free agency and then drafted Teez Tabor (second round) and Jamal Agnew (fifth).

Tabor is expected to compete for time on the outside, Agnew will try to push Diggs in the slot, and Hayden has experience playing both inside and outside.

Quinn is always looking to foster good competition at every position, and it should be fun to watch which three players emerge at the position over the next couple months.

5. Strong safety confidence

Miles Killebrew took every advantage of the limited time he received playing in Teryl Austin's sub packages as a rookie. Austin found a way to get Killebrew on the field in extra safety packages, and Killebrew rewarded him with terrific play.

Killebrew played so well, in fact, it seems to reason he's in line for a bigger role in year two. He's already moved one spot up the pecking order after veteran Rafael Bush was not retained this offseason. The Lions return starters Glover Quin and Tavon Wilson.

The Lions didn't sign a safety in free agency or draft one, which shows real confidence in both Wilson and Killebrew. The real question is whether Killebrew can push Wilson for a starting role opposite Quin.