About 15 minutes after Seattle Seahawks safety Earl Thomas broke his left leg on Dec. 4 against the Carolina Panthers, he received a phone call from Jeremy Hills.

Hills, the founder, CEO and head trainer of The Factory in Austin, Texas, has known Thomas since high school, and the two were teammates in college. In 2015, when Thomas suffered a torn labrum, Hills helped him with his rehab, and the safety didn't miss a game.

This offseason, as Thomas rehabbed from the most serious injury of his career -- a fractured tibia -- he leaned on Hills once again.

Dispirited in the immediate aftermath of being carted off with a broken leg back in December, Earl Thomas has been tirelessly working toward proving he's not finished. Otto Greule Jr./Getty Images

"He didn’t really know how to handle injury because he hadn’t had one [like this]," Hills said. "But I know what that’s like to have your season cut short, and when I called him, he wasn’t in the best mood, to say the least. But what I was trying to avoid was what came next, and that was going into that dark place of, 'This is it. This is over.'"

When Thomas tweeted he was considering retirement, most Seahawks coaches and teammates thought it was just the emotion of the moment. Hills knows all about that. During his last season at Texas, he suffered the same injury that Thomas did, and it ended Hills' college career.

As Thomas was waiting to get X-rays on Dec. 4, Hills tried to tell him what to expect. He told him not to do anything crazy and to keep his emotions in check. Thirty minutes later, Hills saw Thomas' tweet.

"I’m like, ‘You’ve got to be kidding me. We just got off the phone. We just talked about this,'" Hills said with a laugh.

"Being an athlete, your whole identity resides in your play, your performance. That’s who you are and how people view you. And then, when you can just abruptly no longer do that, it can take a toll on you. And he just had to get over that, which he did. He got over it."

Hills said he saw a fire in Thomas this offseason that he's never seen before. Hills usually shuts his gym down on Sundays and relaxes at home. But Thomas wasn't in any mood to sit back and take a day off from his rehab.

"A normal Sunday is me kicking my feet up, watching sports, chilling, catching up on my shows, 'Billions,'" Hills said. "I like to watch TV. That’s what I do. I’m a TV buff. And this guy has me in the gym on Sunday morning.

"We’re not even open on Sundays. And we would be in here in the sauna at 10 a.m. Flexibility and mobility at 11 a.m. Hit some weights. And then he wants to do position work. And I’m like, ‘S---, man.’ I missed church a couple Sundays."

After Thomas suffered his injury, the Seahawks' defense fell apart, allowing 12 touchdowns with just one interception. When Thomas was sidelined, Seattle ranked 30th in opponents' YPA (7.77) and 31st in opponents' passer rating (100.3).

The Earl of Seattle The Seahawks' defense suffered significantly after the loss of All-Pro safety Earl Thomas: When Snaps YPA YPD TDs INTs Passer rtg With Thomas 657 7.01 5.96 7 10 77.8 Without Thomas 480 7.77 6.76 12 1 100.3

According to Football Outsiders, the Seahawks' defense ranked fifth in passing DVOA through the first 11 weeks of last season (Thomas started every game). From Week 12 to Week 17 -- a span in which Thomas played just one quarter -- the Seahawks ranked 30th.

It's not a stretch to say that a healthy Thomas is the biggest factor for Seattle to get back on track defensively.

During stretches in March and April, Hills said, Thomas would arrive to train at 10 a.m. and stay until about 4 p.m.

S/O to @ucheaguh for capturing these great moments with @jhills5 #Work A post shared by Earl Thomas III (@earl) on Apr 2, 2017 at 8:53am PDT

S/O to @ucheaguh for capturing these great moments with @jhills5 #Work (5x All Pro but who's counting) A post shared by Earl Thomas III (@earl) on Apr 2, 2017 at 8:57am PDT

"With Earl, you’ve got to hold him back more than try to get him to believe he can do the next thing or take the next step," Hills said. "I’m watching him grimace in pain and walk with a limp. I’m like, ‘Let’s take a break right here.’ He’s like, ‘No, I’m good. Let’s go.’ So that’s just who he is."

Asked why he believes Thomas is more motivated than ever, Hills said, "In the beginning, when you first hit the league, you feel like you’ve got a lot to prove. But I think this time it’s different. I think this time it’s him having to prove it to himself. He wants to see his reps filmed. He wants to view the film. He wants to rep again. That thought of retirement that crept into his mind, I think it’s f---ing with him a little bit. And I think it’s driving him that he can’t even believe he thought that. It’s driving him, and he’s competing with himself to be better than he was when he left. I think he wants to hit this field and erase all thoughts of that injury."

Hills said Thomas doesn't own a home in Austin. He was just staying at an Airbnb for weeks at a time and focusing on his rehab. Thomas didn't have surgery, but his leg was in a hard cast until the bone healed.

Coach Pete Carroll has said Thomas is on track to be ready for Week 1 of the regular season. But the Seahawks signed Bradley McDougald as a free agent to provide insurance at free safety. And Seattle spent a fourth-round pick on Colorado safety Tedric Thompson.

Thomas has been in attendance with his teammates for the offseason program, and we'll find out this week what he's able to do during OTAs.

"If I can put any kind of Vegas bet right now, then I want to go ahead and put it in for Earl Thomas to be the Comeback Player of the Year," Hills said. "The boy is motivated in a way that I just haven’t seen. Not saying that he hasn’t been motivated, but this is a new level that I haven’t seen. So I’m excited to see what’s next for him."