Jack, the team's second-round pick, will play weakside linebacker in the preseason finale at Atlanta on Thursday. It's not a permanent move -- at least at this point -- but it will give the Jaguars a good look at Jack at a position that he could eventually end up playing regularly.
Jack is eager for the different look.
"It actually kind of simplifies my world a little bit more, which is cool," Jack said. "... I just kind of take it as I'm getting a better understanding of the defense. Knowing Mike and then Will, those are the two linebacker spots, so I guess learning and knowing what's going on is the biggest thing."
The Jaguars started Jack at middle linebacker so he could learn the entire defense, including play-calls, adjustments, and making sure everyone is lined up properly. He missed valuable time in the spring, though, because he was forced to sit out organized team activities due to the NFL's graduation rule. He got a brief introduction during the three-day minicamp in June but was still behind when training camp began.
Jack said the duties at weakside linebacker are similar to middle linebacker, which helps make the transition easier, especially since he'll only have three days of practice at the spot before the game. He might play the entire game, too, because it's likely that Telvin Smith will be among the starters held out -- or plays only one drive.
"I'd say the toughest part is to transition my mind because I've been playing Mike this entire time," Jack said. "It's all I've been honed in on, so now I've got to adapt and figure out the Will spot. It's not much of a difference. I've just got to open up my mind and see the bigger picture.
"I'll just try to really focus on my mental reps and watch film and watch how Telvin does the position and see his issues and how he plays and try to learn from that."
Weakside linebacker is where the 6-foot-1, 247-pound Jack could eventually end up, at least later this season, even though the long-range plan is for him to take over for middle linebacker Paul Posluszny. Sources inside the organization say the defensive coaching staff is not pleased with Smith because he gets himself out of position and that results in big plays. The two long pass plays the New York Jets hit in the preseason opener, for example, came because Smith chased a route he wasn't supposed to and left the middle of the field open.
Jack's strength is his athleticism and coverage ability -- he even lined up against USC receiver Nelson Agholor during a game while at UCLA -- and it wouldn't be surprising to see him and Posluszny on the field together in nickel defense during the regular season instead of Posluszny and Smith. That might be getting too far ahead, though, because right now the Jaguars haven't even seen Jack at weakside linebacker.
Posluszny said he believes Jack will be fine on Thursday.
"To show the coaches that he can do both is really, really cool for him," Posluszny said. "There's a lot of carry-over between the Mike and the Will. We're both off-the-ball linebackers, so there's a lot of carry-over, things he can transfer from one position to the next. He'll be able to step right in, play with a clear mind and be able to play fast.
"It's going to be an interesting challenge but he can handle it."