Perhaps he is a little surly when he has to awaken so early. Perhaps he carries that surly attitude to the practice field. Perhaps that explains why his ferocious play has him bracketed first-team at free safety with junior Dennis Rogan and participating on four special-teams units as the Vols' season opener vs. Western Kentucky approaches.
Although Jackson played well in all three full-scale scrimmages this preseason, he peaked in the last one, held Aug. 22.
"Preseason Game 3 he was phenomenal on defense and he was the best special-teams player of the day," head coach Lane Kiffin noted. "Right now we have him on all four special teams and he started (the situational scrimmage) on defense, as well."
Jackson knew he played well on Aug. 22 but had no idea he'd made such a lasting impression on the coaches.
"No, I just go out there and play," he said. "My game has always been the same. I know whether I do good or not, and I feel like I've been doing good all camp. The biggest thing is for me to keep picking up on the playbook.
"It's a big playbook," he added. "You've got to know where to line up and make your checks. There's a lot of things that come into play on (Monte) Kiffin's defense."
Asked when he began to feel comfortable in Tennessee's scheme, Jackson returned to his recurring theme.
"When I learned the playbook," he said. "When I knew what I was doing before I went out there."
Knowledge of the playbook completed the puzzle for Jackson, who always had the athleticism and aggressive nature to shine - even in the thankless role of covering kicks.
"Every time I go down on a kickoff I try to be the first one down and I try to knock somebody out," he said. "I love kickoffs because everybody on the kickoff is defensive, so it's a defensive-like play."
Given Jackson's hard-nosed nature, it isn't surprising that he has earned spots on Tennessee's kickoff-return, kickoff-coverage, punt-coverage and punt-block units. It isn't surprising that he played on three special-teams units in high school, either.
Still, freshmen routinely show up on special teams. They rarely show up on the two-deep depth chart at a position as mentally challenging as free safety. Clearly, Janzen Jackson is an exceptional talent. He must be to earn a spot in Tennessee's crowded defensive backfield.
"I know we've got a lot of talent back there," he said, "and everybody's going to get a chance to play."
Jackson has a chance to do more than play. With some quality work in practice this week, he has a chance to start. That doesn't surprise him, given what Lane Kiffin told him during the recruiting process.
"He kept his word," Jackson said. "He promised me I'd have a chance to start. He has put me in position to start."
Jackson's closest friend on the team appears to be All-America safety Eric Berry, a good guy to emulate.
"Eric is like my tutor on the field," Jackson said. "When I don't know something, he'll let me know. He's kind of like a big brother out there. Every time he talks I keep my ears open. I don't speak when he does ... kind of like (the respect one shows) a coach."
Like most guys who were high school superstars, Jackson is finding college football a lot more taxing.
"In high school you can take plays off, kind of jog around and still make plays," he said. "In college it's a different animal. You've got to run all the time. You've got to be physical, too.
"Sometimes at my position you'll be locked up with a tight end, and that ain't no joke. A lot of times they'll get with you. They're 6-4 and 200-plus (pounds), so it's kind of hard locking up with those guys."
Still, locking up with tight ends isn't as tough as waking up at 6:30.