It's with a football in his hands, of course, running free with everyone in his wake.
That’s where the second-year Jacksonville linebacker was two weeks ago, when he scooped up a loose ball against the
"I just remember it went quiet," Jack said this week by phone. "That was probably the most peaceful moment I've had in the last two or three years, when I had the ball those first two or three strides. It felt good."
The emergence of Jack is a big reason the Jaguars are having so much success on that side of the ball. He played strongside linebacker as a rookie but was not part of the nickel package, so he came off the field in passing situations.
He was moved to middle linebacker during the offseason, and started training camp that way. But that was a lot to learn, and coaches eventually decided to keep seasoned veteran
That requires a player to be uncommonly versatile — to set the edge for the defense at the line of scrimmage in running situations, taking on bigger tight ends, and then slide inside in nickel where he's often matched against running backs and receivers.
He's a Ford truck on one down; a Ferrari on the next.
"It's really impressive that he's able to do that," Posluszny said. "It takes a unique skill set physically, and a great understanding about the defense mentally to do that. That tells you a lot about him."
Need a reminder of Jack's versatility? Do a YouTube search of his UCLA highlights, where he's blasting into ballcarriers, breaking up or picking off passes, then playing running back and looking like a first-round prospect on offense. He's a physical freak.
"I've known him since he was 12," said UCLA coach Jim Mora, who raised his kids in Bellevue, Wash., where Jack was a high school star. "I've been convinced forever that he could have been a safety, a linebacker, or a running back and probably could have been a first-round pick at any of those positions."
Some NFL teams might have been tempted to draw up some gadget plays using Jack on offense, but the Jaguars want his laser focus trained on learning his linebacker spot. And that's what Jack has done.
"He has taken this second year extremely serious," said his mother, La Sonjia, who lives in Atlanta and is an executive at Cox Communications. "He's the young man who's at home, at his house, with everything laid out and planning his next move. I'll call to say, 'Hey, how's it going?' He goes, 'Everything is great, Mom, but I'm studying my plays. I need to call you back.' "
Jack doesn’t always have his nose in the playbook. He also plays the Madden video game for hours on end, typically assuming the role of the team the Jaguars are playing next. [He said he seldom plays as himself.] He was
“If I’m playing video games I look at it as, I really should be studying but I am kind of studying in a way,” he said. “I’ll be
Goff and Jack faced each other twice when the quarterback was at California, with UCLA winning both times.
"Very cool guy, and from what I remember very accurate," Jack said. "He used to throw the ball at Cal like 70 times a game, so he's been a gunslinger. He was always bringing them back, putting the ball in places that our DBs couldn't get to."
Jacksonville defenders are getting to a lot of footballs these days, and, as he showed on his fumble return, Jack can be plenty elusive when he wants to be.
"Sometimes you see defenders, especially on a long run, you can say, 'OK, I know that's why you play defense,' " Posluszny said. "But with him, it was so natural. The way he held the ball, the angle he took to the end zone, the speed that he had. He was able to peek back and see if anybody was able to catch him. It looked so smooth."
For Jack, it felt even better than that.
"It was kind of like a surreal moment where everything just felt right," he said. "I picked it up and I didn't hear anything. All I could see was just field. I was locked in, tunnel vision. I couldn't really see too much. I just remember being in the moment. It was kind of an out-of-body experience, knowing I was going to score a touchdown and put our team back in the game."
La Sonjia Jack said she had a strong feeling an instant before that turnover that her son was about to make a big play.
"I can tell from the field with his body language when he's on fire," she said. "His head gets to bobbin', and I see him tighten up his gloves, and then I know it's on. I know, somebody better watch out, he's on fire."
Amazing instincts. Like mother, like son.
Follow Sam Farmer on Twitter @LATimesfarmer