The most puzzling unit on the New York Jets is the offensive line. It has produced a couple of terrific games, but it's starting to look as if those were aberrations, especially after the clunker last Sunday in Tampa.

"We had a bust here and there, we missed a few blocks," coach Todd Bowles said of the six-sack debacle. "We didn't play well as a group."

So, what's the deal?

A closer look reveals that, more often than not, the line performs below an acceptable level. We could throw out a bunch of numbers, but the one that really jumps out is the average yards per rush.

First five games: 4.5.

Past five games: 3.6.

You can see where this is headed. Don't be surprised if there's an offensive-line shake up in the offseason, starting in the middle.

When the Jets moved on from perennial Pro Bowl center Nick Mangold, who declined because of injuries and age, they decided to hand the job to understudy Wesley Johnson. Johnson is relatively inexpensive ($2.75 million) and had been groomed for two years, so they figured it was worth a shot. He received a strong recommendation from line coach Steve Marshall.

Johnson is smart and tough, but he's not close to Mangold, who was a strong anchor at the point of attack. While outside ratings are subjective, it's worth noting Johnson has the lowest grade among the 37 qualified centers in the NFL, according to Pro Football Focus.

The Jets have been spoiled at center. From 1998 to 2005, they had Kevin Mawae, a Hall-of-Fame finalist. In came Mangold, one of the best in the sport from 2006 to 2016. Johnson will be a free agent, and it appears the Jets will go in another direction, either via free agency or the draft.

They also need to take a hard look at left guard. James Carpenter was a terrific free-agent signing in 2015 -- one of the best of the Mike Maccagnan regime -- but his performance has slipped. Unofficially, he allowed four quarterback knockdowns against the Bucs and his overall grade for the season ranks 65th of 79 guards (prior to the Monday night game), per PFF.

Carpenter, 28, has another year left on his contract ($6.8 million cap charge), so they can escape without serious cap ramifications. They don't have an heir apparent on the roster -- backup Dakota Dozier will be a free agent -- so any decision on his future likely would be based on potential upgrades outside the organization.

Right tackle is another position that needs to be examined. First-year starter Brandon Shell has held up reasonably well in pass protection (four sacks allowed, per PFF), but is not the kind of overpowering run blocker you need at right tackle. Surely there will be upgrades available in the offseason, but will Maccagnan toss aside a former draft pick?

Because of sizable guarantees, the Jets are virtually locked into right guard Brian Winters ($7 million) and left tackle Kelvin Beachum ($4 million) in 2018. Winters admitted he "didn't play up to my standards at all" against the Bucs (1.5 sacks, two penalties), but his season has been fairly solid. Ditto, Beachum. He's a below-average run blocker, according to PFF, but he's a good blind-side protector (only two sacks).

The Jets haven't invested much draft capital in the offensive line in recent years. In fact, the last time they picked one in the first or second round was 2010 -- Vlad Ducasse, who never worked out. You'd like to say it belongs atop their offseason wish list, but you could make that argument about a few other positions.