The FOX broadcast reported Thomas was taken directly to the X-ray room, and Seahawks head coach Pete Carroll gave reporters the bad news after the game.
"It was a lower-leg fracture," Carroll announced during his post-game press conference.
Thomas, 29, entered 2018 in the final year of his contract, which pays a base salary of $8.5 million. He entered the offseason eyeing a new deal, but the Seahawks remained steadfast in not wanting to renegotiate a contract extension. The fallout resulted in Thomas holding out from all offseason activities, including training camp and preseason action, before he reported to the team in time for Week 1.
The Seahawks started the season 0-2, but have won two consecutive games with Thomas' three interceptions leading the defense.
"We were just turning things around; everything was going in a really positive direction," Carroll told reporters. "It breaks my heart that we're talking about this right now."
Thomas stayed on the ground after the play, and teammates quickly huddled around him on a knee while holding hands. Numerous Cardinals players, including cornerback Patrick Peterson, came over to offer words of encouragement. Medical personnel applied the air cast on Thomas' lower left leg before helping the safety get on the cart.
"I don't know, somebody said something, I don't know anything about that," Carroll told reporters. "It's a big stadium."
Carroll added: "Earl was extraordinarily poised on the field for what just occurred. To be so clear and resolved, he knew what happened. He was so poised; giving back to the players and all of us, so I don't know what happened after that."
Perhaps the gesture was out of frustration over the injury or it could have deeper roots when considering the contentious relationship Thomas and the Seahawks endured during the offseason.
"I was always counting on me and him figuring out where we are going with this thing," Carroll said, according to Gregg Bell with The News Tribune. "I knew it was going to take time, and we didn't have the time when we were together.
"Given the opportunity, we just have so much background and so much history that I thought we could make it, you know. We just talked our way through it, and it made sense with what was coming up. That's what makes it so...makes it so hard, that this is what happened this week."
Carroll re-addressed Thomas' situation Monday morning during a weekly radio spot: "Give him a little slack. This is a very, very difficult moment that most people would never understand what this is all about."
Before the past two seasons, Thomas was a model of durability. He appeared in and started every regular-season game from 2010 to 2015 before missing seven games between the 2016 and 2017 campaigns.
Thomas recorded 28 interceptions -- two returned for a touchdown -- and forced 10 fumbles for Seattle and helped the team secure a win in Super Bowl XLVIII. He is tied for the third-most interceptions in the NFL since 2010 and no safety in the league has earned more Pro Bowl selections than Thomas in the same span.