ESPN Saints reporter Mike Triplett explains why Terron Armstead's signing is the among the Saints' top priorities this offseason. (1:16)

Terron Armstead's new five-year contract with the New Orleans Saints might destroy his reputation as one of the NFL’s best-kept secrets.

Armstead surely did not come cheap (the numbers haven’t been released yet). But the Saints were wise to lock up their 24-year-old left tackle before that secret gets out even more -- and before he was scheduled to become an unrestricted free agent in 2017.

There’s a reason why I keep trotting out what Saints coach Sean Payton said about Armstead last year: “There’s not a left tackle I would trade him for in the league.”

Because I know Payton meant it. That’s not just coachspeak.

The supremely athletic 6-foot-5, 304-pounder is arguably the second-best player on New Orleans’ roster behind the guy he’s being paid good money to protect, QB Drew Brees.

Therefore, the fourth-year pro is arguably the most important building block on the team.

Terron Armstead is arguably the most important building block on the Saints. Joe Robbins/Getty Images

Believe it or not, the Saints have some breathing room under their salary cap in 2017, so it made sense for them to start using that space on a guy they can’t afford to lose.

“Terron had one of the best seasons of any offensive lineman in the league last year, and he did it while dealing with an injury that most players wouldn’t be able to play with,” Saints veteran right tackle Zach Strief said of a significant knee injury Armstead fought through for most of the season. “He’s not only an elite talent, but he’s one of the toughest players I’ve ever been around.

“In my opinion, he’s the best offensive tackle in the league right now.”

As Strief suggested, Armstead is perhaps best known for his athletic exploits. A third-round draft pick out of Arkansas-Pine Bluff in 2013, he holds the NFL scouting combine record for fastest 40-yard dash by an offensive lineman, at 4.71 seconds.

But Armstead impressed his coaches and teammates even more last season by playing when he was less than 100 percent healthy. He missed two games in October with the unspecified injury, then came back and fought through the next nine games despite missing ample practice time.

Of course, the Saints still have plenty of holes and question marks on a team that has dipped below .500 the last two years. They need to keep rebuilding their offensive line (it would help if the offensive tackle they drafted in the first round last year, Andrus Peat, could follow the developmental path Armstead has followed). And they obviously need to keep trying to repair their porous defense.

But the Saints are already halfway through the four biggest items on their to-do list for 2017. Last month, they locked up safety Kenny Vaccaro for an extra year by exercising their 2017 option. That just leaves Brees and Max Unger as core players scheduled to be free agents after the season.

The good news is that New Orleans can afford it. Before Armstead signed his deal, the Saints had more than $50 million in projected salary-cap space for 2017 (with only 37 players under contract). Armstead will eat away at that number, and Brees’ next deal -- whenever it finally comes -- will take an even bigger bite. But even those two big contracts won’t swallow it whole.

A Brees extension seems even more likely after the Saints didn’t add a quarterback in last week’s draft.

And now Brees knows his blind side will be well-protected for the remainder of his career.