NORMAN — For Jacob Lacey, it started as a ‘little’ pain in his leg. The defensive tackle first noticed it shortly after Oklahoma wrapped up spring practices, But Lacey didn’t think much of it and continued with his summer plans.

The pain persisted, and he also started to experience shortness of breath, too. And when Lacey boarded a flight to attend a graduation party for friends in South Bend, he started coughing up blood.

When Lacey landed, he went to the hospital in the middle of the night. There, he was told that the issue was caused by a blood clot that had traveled from his leg to his lungs during the flight.

“(The doctor) said I shouldn’t be alive,” Lacey said during his media availability on Monday. “He looked at me straight up and said, ‘I don’t know how you’re breathing.’ He said I’d probably never play football again. I’m just sitting by myself in that back room thinking, ‘Wow, I’m coming here to see some old friends and try to do the right thing and something got taken away from me.’

“They say plane rides and blood clots in lungs (are) a big no-no. I was one decision away from either going to a graduation party or going to the hospital, and I decided to go to the hospital.”

He was diagnosed with pulmonary embolisms in his lungs, immediately putting his football career in jeopardy.

Lacey was put on blood thinners for the next three months and was not cleared to participate in the Sooners’ summer workouts. When fall camp began in early August, he still wasn’t cleared to play.

"Seeing the guys out there balling and I just physically couldn’t whether I wanted to or not, that was rough,” Lacey said.

While Lacey wasn’t able to participate in fall camp, he continued to work to get his body and mind ready. And the Tuesday before the Sooners’ season opener against Arkansas State, Lacey was medically cleared to play.

“Something that allowed me to be able to play so fast was staying locked-in, staying engaged, taking notes, doing everything I would do like I was playing,” Lacey said. “So that just allowed me to be where I’m at today.”

Where is he at today? Well, he’s become an important part of the Sooners’ defense.

Lacey, a former Notre Dame transfer, has played 148 snaps this season, the 13th most on the team and the second most at defensive tackle behind Jordan Kelley, per Pro Football Focus. He’s also started each of the last five games, and he’s totaled 10 tackles, 1.5 tackles for loss and one sack on the season.

That sack came at a critical time.

With the Sooners’ locked into a tie game with Texas earlier this month, the Longhorns drove down the field late in the fourth quarter. Lacey came up with a critical first-down sack, which helped force the Longhorns into a field goal. The Sooners’ offense, led by Dillon Gabriel, then scored on a game-winning drive to seal the win.

Lacey, who was also named a team captain for the game, played a huge role in helping the offense get the ball back with a chance to win.

“(It was a) really big moment for him and certainly if you go back and reflect on it now, who would have thought,” OU coach Brent Venables said.

It was a big moment considering how ‘scary’ it was to hear Lacey’s initial diagnosis.

“I’ll be honest: when he got the first initial diagnosis, you hear the doctors and you hear, ‘Here’s kind of the plan.’ But for our staff, our mindset was, 'Alright, we’ve really got to move on without him and plan on him not being able to make it back to play,” Venables said.

“It’s scary, really scary. Just thankful that under the circumstances, he was diagnosed and went through the right protocols to get him healthy. Fortunately for him and for us from a football standpoint, it was the best-case scenario when it comes to blood clots. I think the minimum amount of time (for recovery), he was one of those (players) that fit into that category. And then between his own mindset and his family’s, what he wanted to do, he was very aggressive in wanting to come back sooner rather than later.”

For Lacey, it was a really tough period following that diagnosis. But that performance against Texas was further proof that he’s gotten through it.

“It meant a lot to me especially because of the stuff I’ve been through recently,” Lacey said. “Just battling back, it just kind of solidified the things that I believed in, that hard work always pays off. Just seeing that and then also playing well in a game like that, it was very rewarding.”