The Jaguars haven't declared a starter at left tackle or left guard and are relying on former right guard Brandon Linder to play center for the first time.

Don't underestimate those issues as much as many outside observers - and even some inside the organization - have done. Offensive coordinator Greg Olson certainly isn't.

"We have a couple of issues we have to get solved," Olson said. "I think we have a pretty good feel about the right side and the center position now. The left side of the line will have some competition. We'll try and make a decision early in training camp."

The two major decisions: When Kelvin Beachum is cleared from last year's ACL injury, how quickly will he supplant Luke Joeckel at left tackle? And if that happens, what is Joeckel's role? Expect those to be answered in time for the Aug. 28 preseason game against Cincinnati.

The secondary decisions: Will the Jaguars stick with Josh Wells and/or Tyler Shatley as developmental backups or keep veterans such as Jeff Linkenbach and Patrick Omameh? We might not get that answer until the final cuts.

What is required for the Jaguars to be competitive is much better play up front. Inconsistency and instability have been two hallmarks for the offensive line since coach Gus Bradley was hired before the 2013 season.

� The Jaguars have allowed 172 sacks, most in the NFL during that span; the next closest is Miami at 149.

� Their 21 rushing touchdowns are second-fewest in the NFL, ahead of only San Diego (19).

� Linder will be the fourth center in as many years, following Brad Meester (2013), Luke Bowanko (2014) and Stefen Wisniewski (2015).

� Whoever starts at left guard will be the third to play that spot, following Uche Nwaneri (2013) and Zane Beadles (2014-15).

� Marrone is the first returning offensive line coach - George Yarno (2013) and Luke Butkus (2014) lasted only one season each.

The Jaguars enter camp feeling good about three of the five positions - Linder, right guard A.J. Cann and right tackle Jermey Parnell.

Linder was the Jaguars' best lineman as a rookie in 2014, but was lost last year after only three games because of a shoulder injury that required surgery. And instead of pursuing free agent Alex Mack or re-signing Wisniewski, the Jaguars decided to move Linder to center.

"The toughest transition on an offensive line is going from tackle to guard or going from tackle to center - it's not as difficult going from guard to center and he has very good foot speed, which is something you need there," Marrone said. "He's done everything extremely well."

The Jaguars feel similarly confident about Cann, last year's third-round pick. He replaced Linder and will remain at right guard. Cann is strong, physical and savvy.

"The No. 1 thing I liked about A.J.'s first year was his toughness," Marrone said. "We just really threw him in there. He would admit he made some mistakes and then we got to see how he [responded] and I thought he did extremely well - he let the mistakes go, he learned from them and he got better and better as the season went along."

On Cann's flank is Parnell, who should benefit from his first full season as a starter.

"Really, Jermey is no different from A.J. as far as game experience, and when you go through a whole season for the first time, you learn how to structure your week - how you want to eat, how you want to take care of your body and how to mentally prepare," Marrone said. "He missed some crucial time [in the offseason with a broken hand], but hopefully we'll be able to make that up in training camp."

Now back to the issues.

Joeckel allowed a team-worst 10 sacks last year and had trouble handling speed rushers. The Jaguars acted by signing Beachum from Pittsburgh despite his ACL injury that has so far kept him off the field.

If Beachum is healthy, well, he's not here to sit on the bench or start at another spot. He'll be the left tackle.

"He's someone who has played at a very high level against very good competition," Marrone said. "He basically does a lot of things well overall."

Beachum at left tackle would mean Joeckel is a backup swing tackle, back-up guard/tackle or starting left guard. Mackenzy Bernadeau took the first-team snaps at that position in the offseason program.

On sliding Joeckel inside, general manager Dave Caldwell said: "It's an option or he wouldn't have taken snaps there [this spring]."

Lower on the depth chart, the Jaguars have been enamored with Wells (a tackle) and Shatley (a guard/center) since they were signed as undrafted free agents two years ago. But they have no NFL starts. They would appear to have the edge entering camp over Linkenbach (36 starts) and Omameh (25 starts), who were signed after the offseason program started, but could emerge.

Tuesday: Defensive line.

Ryan O'Halloran: (904) 359-4401