The Jets are all in for 2019.

On Thursday, they signed former All-Pro Panthers center Ryan Kalil, who had retired after last season, as a potential major upgrade in the middle of the offensive line.

Kalil was lured out of retirement by new Jets general manager Joe Douglas with a one-year, $8.4 million deal with more possible in incentives, according to NFL Network.

Kalil, who made $7.5 million last season in Carolina, was scheduled to take a physical at the Jets’ training facility in Florham Park, N.J., on Friday. If he passes, he will make his practice debut Saturday.

The 34-year-old Kalil, who had spent his entire 12-year career with the Panthers, played in all 16 games in 2018 (97 percent of the snaps), but was limited by injuries to just six games in 2016 and eight in 2017, when he suffered a significant neck injury.

This is the most significant move yet for Douglas, who was hired in June after free agency and the draft. And it is a big plus for second-year Jets quarterback Sam Darnold and star running back Le’Veon Bell.

The Jets had appeared set to go into the season with Jonotthan Harrison as their starting center. Harrison has 26 career starts at center, but mainly has been a backup the past five seasons. The Jets had interest this offseason in former Broncos center Matt Paradis, who signed with the Panthers to replace Kalil, and also pursued center Mitch Morse, who signed with the Bills.

On Monday, Jets coach Adam Gase offered praise for Harrison, saying he and Darnold had “a good relationship’’ and “have done a really good job of taking control of the offense and really kind of putting their spin on it. The communication is outstanding between those two.”

Kalil, a second-round pick by Carolina in 2007, is a two-time first-team All-Pro and five-time Pro Bowler. He has played in 148 NFL games, making 145 starts.

Last season, Kalil graded out as 17th among all NFL centers, according to Pro Football Focus. Harrison was ranked 31st. Spencer Long, who spent most of 2018 starting for the Jets and had curious issues with shotgun snaps, ranked 38th.

Center has been a major weakness for the Jets since Nick Mangold retired after the 2016 season after manning the position for 11 years. Wesley Johnson had a highly underwhelming season as the starter in 2017 and Long was even worse last season.

Mangold tweeted his approval for the Kalil signing Thursday afternoon, saying, “This is pretty cool. Welcome @ryankalil.’’

Earlier this offseason, the Jets added former Raiders All-Pro left guard Kelechi Osemele, who was signed as a free agent in March. The three other starters on the line — guard Brian Winters and tackles Kelvin Beachum and Brandon Shell — return from last year’s group.

Douglas has spoken since he was hired of the importance of building a top offensive line. With this Kalil acquisition, he’s put his money where his mouth is.