This is the fourth in a series of stories that’s examining the Packers’ roster, position by position, leading up to the 2016 draft. The series continues with the offensive line.

GREEN BAY – The stability the Packers have enjoyed on their offensive line in recent years may not last much longer.

As they enter a third consecutive season with the same starting five up front, the Packers have three of those starters – left tackle David Bakhtiari plus guards Josh Sitton and T.J. Lang – entering the final year of their current contracts.

That’s not to say all will depart after 2016, but salary-cap considerations could make it difficult to bring back all three. That makes the upcoming draft a key one for building depth and finding future reinforcements.

The top priority is tackle, where the Packers nearly saw their season derailed when Bakhtiari was injured last December. It wasn’t until the coaching staff turned to JC Tretter – the third different fill-in over three weeks – to replace Bakhtiari in the playoff opener at Washington that the pass protection finally settled down.

Tretter did an admirable job, but his future is at center, not left tackle, so a bona fide backup for both tackle spots is needed. Veteran Don Barclay, who struggled in his return from ACL surgery last season, and practice-squad holdover Jeremy Vujnovich are the only pure tackles currently on the roster outside of starters Bakhtiari and Bryan Bulaga.

Ideally, the Packers will find a swing tackle in this draft who can help reinforce both sides in 2016. Bakhtiari’s missed starts in 2015 were the first of his career, but Bulaga missed four games as well.

With another tackle on board, the Packers will feel well-stocked at the position at least through the end of Bulaga’s current deal if they’re able to re-sign Bakhtiari. If not, then a potential replacement is already being developed and learning the system.

At the inside positions up front, the need isn’t as pressing, but the possibility of losing both guards in free agency a year from now would give any team pause. Both Sitton and Lang are tough, leader types who have played through multiple injuries in recent seasons. Sitton is a Pro Bowler while Lang is perhaps on the verge of that level, provided he returns to full health from offseason shoulder surgery.

Backup Lane Taylor was re-signed this offseason, and two undrafted rookies from a year ago in Josh Walker and Matt Rotheram also return with an important year under their belts, so depth at guard is present, for now. Whether during or after the draft, expect more young linemen to be brought in to compete for roster spots with an eye toward a possibly changing future at the position.

At center, Tretter held up just fine for three starts in place of an injured Corey Linsley last season, but Tretter is now in the final year of his rookie contract as well. If the Packers are committed to Linsley long term, Tretter may use free agency to find a place he can start in 2017, which puts a developmental center on the radar, too.

View previous stories in the position-by-position breakdown

QB: Drafting another not out of the question

RB: Future not entirely clear for Packers

WR: Playoffs changed Packers' outlook