He returned to practice just last week and made his pro debut four days later. Rather than pity himself during the injury, Thornton used the down time to improve.
"I think I had to learn how to become more professional and take some mental reps and change the way I studied film and just looked at the game," he said. "When I came back, I made some mistakes. They were easy to correct. The guys were helping me out throughout the whole game."
Now that he's back on the field, Thornton wants to make his playing time just as productive.
His lack of training camp practices robbed him of some conditioning time, and he said he must improve his recognition of defensive tricks such as line stunts. He's also working on his chemistry with his teammates and becoming more comfortable with his role.
That might seem like a lot to accomplish with the regular-season opener looming Sept. 8. But Thornton already has made up a lot of ground.
The third-round pick saw playing time with the first unit against the Browns — even though veteran Jeff Linkenbach got the start in place of McGlynn — and seemed to make the most of it.
"I would have been happy wherever they put me," Thornton said. "I'm just glad to be out there playing football again after coming here with high expectations for myself and for the team. And just being able to be with that group and the group trust me enough to help out and play with me, it was an awesome feeling."
Whatever chance Thornton had to compete with McGlynn for the starting job likely was erased by his training camp absence. But McGlynn's own injury has again opened the door a crack.
Thornton likely will get another extended audition against the Bengals, and if all goes well he'd be the first in line if McGlynn's recovery unexpectedly lasts past the regular-season opener against Oakland.