Alex Vlasic thrived playing across the ice from Seth Jones in his first full season with the Chicago Blackhawks. Now Vlasic will get the opportunity to play alongside the veteran for the next six seasons.

The 6-foot-6, left-side defenseman agreed to a $27.6 million contract extension that runs through 2029-30 — the same as Jones’.

The last two seasons of Vlasic’s deal — which carries an annual $4.6 million salary-cap hit — contains a modified no-trade clause with a 10-team no-trade list, according to Capfriendly.com.

“I took a lot of big steps and improved my game,” Vlasic, 22, said during end-of-season interviews last week. “I think coming in, I didn’t know what to expect of myself and I think I kind of exceeded my expectations of what this year was going to look like for me and I’m very happy with it.”

Vlasic had been a restricted free agent with arbitration rights, but the Hawks opted to take care of business quickly.

“Alex made enormous strides this year and proved he is a legitimate top-four defenseman in the NHL,” general manager Kyle Davidson said in a statement. “In his first full season in the NHL, Alex established himself as an important piece of our young core, and we’re excited to have him with us for the next six years.”

And at nearly $28 million over the life of the contract, it’s also general manager Kyle Davidson’s largest signing by far since taking over on an interim basis in October 2021. Connor Bedard’s three-year, $13.35 million entry-level deal is the next largest.

Vlasic, a Wilmette native, had said he wanted to stay in Chicago “as long as possible.”

It’s clear that Vlasic joins Bedard as part of the young, long-term nucleus that’s beginning to take shape, along with defenseman Kevin Korchinski, forward Frank Nazar and others.

For a team that finished 23-53-6 — the most losses in franchise history (topping the 1953-54 season’s 12-51-7) — it’s a light at the end of the tunnel.

Vlasic took a big jump this season, particularly as a lockdown defender.

According to analytics sites JFresh Hockey and TopDownHockey, Vlasic’s even-strength defense rose to the 94th percentile, his penalty kill to the 90th percentile.

And he was doing it facing top competition (94%).

“He’s played top matchups every game all year, big minutes, he’s playing physical and he moves the puck very well,” coach Luke Richardson said earlier this month. “Now he’s starting to show some of the maturity already on the bench and on the ice, taking charge, talking to the forwards about certain situations and maybe even giving them a little bark down the bench.

“Being in a top pairing role with Seth, I think they really complement each other well. And with their range and with their reach, I think they really defended well. But both of them at times can get up the ice and add into the offense.”

Jones, who play with Vlasic at the IIHF World Championship in Czechia next month, added: “You’ve seen him from early on this year move his feet, defend hard. He’s got a really long stick, so it makes it really tough on defenders. He’s shooting the puck a lot more.”

Vlasic had two goals and 14 assists, and his 16 points was second among Hawks blue liners, a point ahead of Korchinski.

Vlasic admitted his performance surprised even himself.

“A little bit, yeah,” he told the Tribune this month. “I always believed in myself. I knew I could be a good player. I feel like I get more comfortable with repetitions and more games.

“The more games I’ve been playing, I get more confident. I’m able to try new things and see what I’m capable of getting away with and not getting away with. But it’s been a great learning experience. That’s kind of big for me, learning what I can and can’t do out there and continue to push myself.”