PITTSBURGH — Marcus Gilbert should have spent this offseason thanking the Pittsburgh Steelers for their generous contract extension allowing him to retire a Steeler. His play was setting the stage for that celebration. Former offensive coordinator Todd Haley called Gilbert the best right tackle in football during the 2016 season.

Instead, Gilbert’s career in Pittsburgh ended with a two-paragraph news release on March 13 announcing that the Arizona Cardinals had acquired Gilbert in exchange for a sixth-round pick.

What happened between Haley’s comments and the ho-hum transaction shook Gilbert to his core, leaving him to process guilt over a career suddenly marred by curious injuries, a suspension and unmet expectations.

“I felt like I disappointed a lot of people in Steeler Nation,” Gilbert, a free agent in 2020, told ESPN in an interview shortly after the trade. “It hasn’t been easy.”

Therapy sessions, fatherhood and the potential for rejuvenation in the desert now have Gilbert vying for his spot at age 31.

He could deal with missing five games due to hamstring issues in 2017. And, sure, that drug suspension that cost him four games and $1 million later that season was bad — Gilbert said he failed to follow protocol when refilling a prescription he had taken for years — but at least he returned for the late-season push.

But a partially torn quad injury started an avalanche of emotions in early 2018. Gilbert said a “total freak accident” happened during a routine move in practice sometime around the Week 7 bye. Steelers trainers thought Gilbert had tendinitis until an MRI revealed more, he said.

Surgery would have shut him down for the year, so he opted for a stem cell shot to trim recovery time.

He rigorously rehabbed for a December return but sensed that fans were turning on him. He found himself scrolling through his phone at night, unable to ignore the vitriol on social media.

“When you go from playing at a high level, then you’re not out there on the field, and you’re getting a lot from the fans, the coaches and teammates can’t rely on you because you’re not out there — all those things mount, and it’s tough,” said Gilbert, who played eight seasons with Pittsburgh. “Nasty tweets, lots of questions, and you read the articles. Athletes can say that doesn’t bother them, but you see it.”

He classified his overall mood as “down,” especially around the house. He is a father to son Maverick, who is almost 1, and didn’t want his family life compromised.

Therapy helped him cope with the harsh realities of NFL business. Gilbert had explored it in the past, and committing to a weekly regimen last year proved effective.

The Steelers placed Gilbert on injured reserve on Dec. 15, despite his feeling ready to play. Matt Feiler was playing well at right tackle, and Gilbert’s tenure in Pittsburgh was all but over.

He remembers the simpler days of football, kicking butt with friends and enjoying the locker-room camaraderie. He still values those things, but he knows juggling the physical toll of the sport with high-level business and adulthood can be a challenge.

“We are athletes, and we do deal with a lot,” he said. “Knowing the high stress level we go through, it’s always a good thing to get a professional point of view from the outside. I’m a firm believer in it.”

Gilbert doesn’t focus on the math, but it’s safe to assume that the injuries cost him millions. He has one year left on a five-year, $30.8 million contract, which is below market based on the height of his skills. For comparison, offensive tackle Chris Hubbard, Gilbert’s long-time backup, earned a five-year, $36.5 million deal with the Cleveland Browns last offseason.

Gilbert remembers the Steelers assuring him that he’d be their right tackle in 2019, but his age coupled with $4 million in cap savings from the trade made him expendable.

It wasn’t supposed to happen this way, he says. One of the best offensive lines in football wanted to remain intact. Maurkice Pouncey and Ramon Foster reupped in March. Alejandro Villanueva and David DeCastro are under contract for multiple years.

Gilbert isn’t bitter, he says. He has become better at acceptance.

“You can never be surprised with NFL business,” he said. “They respect me, but you have to understand it’s a business. I didn’t take it personally.”

Those online criticisms that once engulfed him now motivate him, with Gilbert telling himself, “I want to show them what they have been missing.”

The Cardinals offer a safe landing spot and a dose of excitement from general manager Steve Keim, who told Gilbert that his stellar game tape made the trade an easy call.

Gilbert also reunites with offensive line coach Sean Kugler, who was on Pittsburgh’s staff when the team drafted Gilbert in 2011.

“Once I get on the field, I’ll have my play speak for itself,” Gilbert said. “I feel like I have a lot of time left. I want to take on more of a leadership role.”

He plans to train for an injury-free 2019, reclaiming his spot as one of the best at his position.

That is, when he isn’t putting Maverick on his shoulders at home.

“There’s no better joy than being a father,” he said.