A high ankle sprain suffered by Jacksonville Jaguars' middle linebacker Paul Posluszny in the team's overtime loss to the Indianapolis Colts lost Sunday forced rookie Thurston Armbrister into the lineup.

Armbrister, an undrafted free agent out of the University of Miami, entered the game against the Colts having only played on special teams. When Posluszny went out, Armbrister took over, playing 38 snaps on defense. He assisted on two tackles in the loss.

"There was a lot of pressure on me,'' Armbrister said, per Vito Stellino of the Florida Times-Union. "At first, I was kind of nervous, but I realized what I came here for and that the coaches had a lot of trust in me to put me in there in charge of the defense."

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Despite a few mistakes, Jaguars head coach Gus Bradley said Armbrister handled the opportunity well.

"The big thing was run fits,'' Bradley said. "Just a few assignment errors, but he'll learn from that. I thought overall for getting thrown in like he did he did a pretty good job.''

The Jaguars are holding out hope Posluszny will be able to play Sunday against Tampa Bay. If not, Armbrister will get the start.

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