Nearly six months later, the images of Alabama running back Najee Harris in college football’s national-championship game remain vivid: bursting into the open, bouncing off tacklers, making a loud splash on the sport’s biggest stage.

Now he’s eager for an encore.

Harris, the country’s No. 1 recruit in the class of 2017 at Antioch High School, peers toward the start of training camp early next month with a curious mix of bravado and skepticism. His six-carry, 64-yard performance in the title game might have showed the world his readiness, but he already brimmed with quiet confidence.

That’s why he contemplated leaving Alabama after his freshman season, frustrated by sparse playing time. And that’s also why he ultimately stayed, figuring Alabama still offers the best path to the NFL.

Harris wasn’t allowed to talk to the media as a freshman, per school policy. But he sat down with The Chronicle during a recent visit to the Bay Area, to reflect on his inaugural year in college and look ahead to the upcoming season.

“The only thing I can tell you is, I hope I’m on the field more,” Harris said. “Last year was the worst feeling. That whole season was mentally challenging.”

Harris grew up on the West Coast, bouncing between the Bay Area and Seattle before settling in Antioch for his high school years. He became accustomed to smoking-hot summer days on the delta, but it’s not the South.

Harris spent much of last summer and most of this June in Tuscaloosa, Ala., immersed in training, and he routinely awoke at 5 or 5:30 a.m. for workouts. His first step outside still reminded him he was no longer in Northern California.

“It’s humid as hell, man,” Harris said, a sense of wonder in his voice. “We don’t have anything like that here. I’m telling you, that humidity over there in the summer? That’s no joke.”

The weather might count as the biggest difference, but Harris soon realized the abundant contrasts between the Bay Area and Alabama. People are nicer in the South, he said, but he likes California food much better. He struggles to find good Chinese or Mexican food in Tuscaloosa.

“It’s different,” Harris said of life in Alabama. “I’m still getting used to everything. It’s a slower lifestyle than California.”

He doesn’t have as many friends as he does back home, though he quickly became tight with several other freshman teammates last season: quarterback Tua Tagovailoa (his roommate) and offensive linemen Alex Leatherwood and Jedrick Wills.

Harris struggled academically at times in his first semester, then learned how to handle his schoolwork. He changed majors from business to social work and, as he put it, started paying closer attention in class.

Another enduring and not-at-all surprising lesson during his first year in college: Alabama football players are powerful, full-fledged celebrities in Tuscaloosa. Strangers inevitably want photos, and players routinely jump to the front of the line at restaurants and bars.

Harris, reserved by nature, insisted he’s not interested in the trappings of celebrity and gladly “chills” at the back of the line. He dresses quickly after games and tries to avoid the customary clamor for autographs and photos.

“I don’t go around dressing up all nice, like a lot of people — designer chains, diamonds, gold, all that stuff,” he said. “No, bro. I just walk out with my headphones on, head down, and I’m the first one on the bus.”

His offseasons in Tuscaloosa revolve around workouts — running, weight training, balance drills, treatment — and summer-school classes. Harris occasionally returns to Alabama’s lavish football facility for extra work, prompting team trainers to tell him to slow down.

That’s a refrain he heard in high school, too, but Harris loses himself in physical conditioning. He was similarly committed during a three-week stay in the Bay Area in May, driving each morning from Fairfield (where his girlfriend, Olivia Petnicki, lives) to Antioch to work with longtime personal trainer Marcus Malu and track coach Josh Tezeno.

Harris has noticeably broader shoulders and thicker arms than he did as a high school senior. He has zero percent body fat, he said, and carries about 230 pounds on his 6-foot-2 frame. He also increased his bench press to 365 pounds, according to Malu.

“I’m so determined,” Harris said. “I can’t have fun unless I achieve my goals, or else I’ll be thinking about that the whole time.”

Harris relished his team’s national title, but the Crimson Tide’s 26-23 victory over Georgia in overtime Jan. 8 also punctuated what he called a “draining” freshman season. That’s why he zipped home to the Bay Area later that week to huddle with Malu.

Malu and another friend, Mori Suesue, listened to Harris’ frustration over his lack of playing time and encouraged him to stay at Alabama. Harris’ mom, Tianna Hicks, offered similar advice.

And so, after mulling it over for a few days, he returned to Tuscaloosa.

“I told him there’s not another school that is going to prep him as well, and give him the competition every day to get him ready for (playing on) Sundays,” Malu said of their conversations in January. “He was just down. I said, ‘You have to go back. I know you’re down right now, it happens. But you have to go back.’

“He needed the mental battles, so he can stay focused and hungry. I told him, ‘You’ve always been the hardest worker, and now you’re in a room full of hard workers. Nobody remembers what you did all year, they remember the yardage you gained in the title game.’”

Harris had two 70-yard rushing games early in the season, in blowout wins over Fresno State and Vanderbilt. He barely saw meaningful action in the second half of the season, until head coach Nick Saban abruptly inserted him in the fourth quarter of the national-championship game. Harris quickly ripped off runs of 16, 35 and 11 yards.

Tagovailoa understandably received credit for sparking Alabama’s comeback, but Harris played a strong supporting role. He was “running angry,” as he told Malu, because he felt he regularly outplayed other running backs in practice — often breaking long runs — and still had to wait his turn behind more experienced players.

Harris met with then-running backs coach Burton Burns after the season and had two one-on-one meetings with Saban in the spring. Saban reminded Harris he needs to polish his pass-blocking skills, he said, though Saban also acknowledged Harris’ frustration and told him, “You’re going to play a lot this year.” (Saban was unavailable for comment, according to an Alabama spokesman.)

That seems likely, given the way Harris played in the title game. He still faces stiff competition at Running Back U: Bo Scarbrough, last year’s starter, departed for the Dallas Cowboys, but senior Damien Harris and junior Josh Jacobs are still around.

Najee Harris is second-string on most projected depth charts, behind Damien Harris and either ahead of Jacobs or sharing the No. 2 spot with him. The Tide often rotate their backs, dividing carries among the top two or three.

Harris’ mom moved from Antioch to Birmingham to be closer to her youngest son, but he maintains ties to his former community. He returned to the Bay Area last weekend and spent Saturday afternoon working at Malu’s “purpose-filled youth outreach” at Los Medanos College in Pittsburg.

The event provided athletic camp-style training for about 70 kids, plus motivational speakers and counseling on decision-making skills. Harris worked with kids on the football field, running them through drills in 95-degree heat.

He was scheduled to head back to Alabama on Wednesday for his own summer training. He seems conflicted, knowing Saban’s powerhouse program is a springboard to the pros but also impatient for his chance to thrive.

Harris seized the day Jan. 8 — carpe diem, as the saying goes — and now he’s restless for another day, another big stage, another loud splash.

Ron Kroichick is a San Francisco Chronicle staff writer. Email: rkroichick@sfchronicle.com Twitter: @ronkroichick