All you once needed to know about Titans tackle Taylor Lewan’s high regard for the life and limb of Marcus Mariota was contained in a YouTube clip in 2017.

When Seattle’s Richard Sherman laid a late, crunching out-of-bounds hit on Mariota in an early-season game that year, Lewan’s sudden fury propelled the 6-foot, 7-inch 310-pounder across the field, where he immediately cornered Sherman, face mask to face mask, before they were pulled apart.

The abridged, G-rated version, accompanied by much finger-pointing, was something along the lines of, “You can’t have that on my quarterback. That’s my guy. That’s our guy.”

It would not be the first — or last — time Lewan took on the role of enforcer in attempting to protect Mariota.

Which was why Lewan’s social media video post Wednesday that he was facing a four-game suspension for failing a drug test under the NFL’s policy on performance-enhancing was so jolting.

A handful of players test positive every year, of course, but not usually All-Pro left tackles whose avowed mission is to protect the blindside of the right-handed franchise quarterback. Not ones who have sworn a Pontifical Swiss Guard-like oath to protect their man.

It is an assignment that Lewan seized upon when Mariota first came aboard and took obvious pride in, so tight had their bond become. And it is a role he has been richly rewarded for performing at a Pro Bowl level with the five-year, $80 million contract extension that made him the league’s highest-paid offensive lineman.

That Mariota still enjoys mobility, after being bounced around like a crash test dummy with 130 sacks in four years, is probably attributable to what Lewan provided.

This year, finally, it was starting to look like the Titans were committed to doing something about it with the addition of free agent Rodger Safford to line up next to Lewan at guard, bolstering the left side.

But if a four-game suspension of Lewan is upheld (he can appeal), the Titans and Mariota would have to do without their best blocker for games against the Browns, Colts, Jaguars and Falcons.

That’s a concern on several levels. For one, this is supposed to be a year that the Titans raise their game and make a playoff run, and having Mariota remain upright and healthy is a key part of that.

For another, this is Mariota’s make or break year, the season that is projected to determine whether the Titans invest in a lucrative long-term contract to keep him or look elsewhere.

In Wednesday’s’s video, Lewan tearfully maintained that he had not knowingly taken the banned substance ostarine, calling it “a complete accident.” He promised to post results of a polygraph test he said he took to back up the contention.

Lewan said his doctor and nutritionist look into what he was taking and that he passed a drug test in April but failed one on May 28.

The U.S. Anti-Doping Agency website reads, “There are in fact products that contain ostarine, but only illegal ones.” It adds, “However, you should be aware that some dietary supplement manufacturers illegally put SARMs like ostarine in their products and sell them as ‘legal steroids’ or ‘research only’ chemicals. Moreover, they may omit ostarine from the label entirely, or use misleading names to confuse consumers.”

Whether you choose to believe Lewan’s contention or not, Mariota, the former Oregon Duck, is now at risk of becoming a sitting duck.

Reach Ferd Lewis at flewis@staradvertier.com or 529-4820.