Tanner McCalister got a lot of questions at the start of this year.

After the safety transferred to Ohio State in January, his teammates were curious about Jim Knowles, their new defensive coordinator. McCalister had experience with him. They spent the past four seasons together at Oklahoma State.

“Anything they asked, I answered,” he said.  

They continued to pepper him with questions in spring practice. As the defense was installed, players asked if he could stay after practices to review film with them.

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McCalister recalled one instance when he received a text message at almost midnight about a play call out of a specific formation.

His teammates' desire to absorb the new system left McCalister with a feeling of appreciation. It reflected their determination after falling short of reaching the College Football Playoff the previous season.

“Everybody wants to be the best,” he said, “and they want to learn, which is great.”

The role of McCalister for Ohio State’s rebuilding defense has been significant. His presence helped reduce the learning curve for the Buckeyes, who have allowed only one touchdown through their first two games.

“It's like a coach on the field,” coach Ryan Day said. “That certainly shortened the time of learning the scheme.”

McCalister's mother, Alice, noticed an unselfishness from him in high school. Her son tutored elementary school children, spoke to youth football teams and volunteered at their church without the typical resistance of a teenager.

“He was just a guy, that if you asked him to do something, it wasn't like, 'Man, I really don't want to do it,’ ” she said. “He was very happy to do it.”

McCalister’s ambitions at Ohio State, though, extend beyond being a source of playbook knowledge.

He sought to join a national championship contender, giving the Buckeyes a steady presence as their primary slot defender after they featured a revolving cast of nickel corners and safeties in previous seasons. He also brought and versatile coverage skills to cover multiple types of receivers. With an additional season of eligibility, he also hopes to move up NFL teams’ draft boards next spring.

“That’s why he came here,” Knowles said. “He wanted to improve his game.”

“It's cool my teammates trust me to be that quote-unquote ‘coach on the field,’ and the coaches trust me,” McCalister said, “but at the same time, I’m here to make some plays. I’m here to improve my draft stock. And then obviously do all I can to help us get to where we want to be as a team, and that's to win a national championship.”

Before becoming an integral part of the Buckeyes’ secondary, McCalister imagined being a running back.

His bedroom walls in the Dallas suburb of Rockwall featured a Fathead poster of LaDainian Tomlinson, who grew up in Waco before becoming a Pro Football Hall of Fame running back.

On youth league teams, he wore No. 21, the jersey number donned by Tomlinson in the NFL.

“I was an offensive guy,” McCalister said. “I wanted to score touchdowns, run the ball, stiff-arm guys.”

It wasn’t until he joined the varsity team as a freshman at Rockwall-Heath High School in 2014 that he saw a future on defense.

Mickey Moss, then the Hawks’ coach, placed him at cornerback to fill a hole in the defensive backfield. He also felt it was a long-term fit.

McCalister was thin in high school, weighing tens of pounds below the frame of top running back prospects. Almost a decade later, he remains below 200 pounds.

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It was one of the reasons Moss thought he would be more durable as a cornerback or safety.

“You’ll be delivering hits instead of taking hits,” McCalister recalled hearing.

McCalister at first learned a lot from DeShon Elliott, who was a senior when he was a freshman and was a budding safety prospect. Elliott since went on to become an All-American at Texas and a starter in the NFL, where he’s now with the Detroit Lions.

“He was a great player to play under,” McCalister said, “and he kind of took me under his wing.”

The two of them remain in touch, and McCalister got advice from Elliott last winter when he was looking at transfer options.

McCalister didn’t give up playing running back, though, until he enrolled at Oklahoma State in 2018.

He would line up on both sides of the ball at Rockwall-Heath. When he was a sophomore, he was featured in two-back sets with his older brother, Tyler. He saw nearly 200 carries as a senior, rushing for 1,329 yards and 15 touchdowns, in addition to his role at cornerback and safety.

“He carried the load,” Moss said, “and he didn’t shy away from it.”

Moss recalled games in which McCalister played every snap on defense and ran for more than 100 yards, feats rare for the highest division of high school football in Texas.

The Hawks relied on his playmaking.

“For us to be successful, we needed him on the field,” Moss said.

McCalister committed to Arkansas before his senior season at Rockwall-Heath and looked forward to becoming a cornerback in the Southeastern Conference. But after the Razorbacks fired coach Bret Bielema in late 2017, it prompted McCalister to decommit. He signed months later with Oklahoma State, where he would be introduced to Knowles.

When McCalister put his name in the transfer portal in December following four seasons with the Cowboys, the first person he heard from was Knowles, who had left Stillwater to become Ohio State’s defensive coordinator.

The Buckeyes are selective with plucking players out of the portal, often adding only a couple of transfers each offseason.  

But McCalister drew plaudits from Knowles and star receiver Jaxon Smith-Njigba, who also grew up in Rockwall.

Smith-Njigba’s older brother, Canaan, was Rockwall-Heath’s starting quarterback when McCalister was a junior before pursuing a career in baseball. He debuted in the major leagues this season with the Pittsburgh Pirates. Their families are close.

The praise left Day with belief that McCalister could be a key part of Knowles’ safety-driven defenses.

“He's a veteran,” Day said. “He's an experienced guy, but he fit our culture just by the way he immediately stepped in and has been really helpful to the guys.”

Joey Kaufman covers Ohio State football for The Columbus Dispatch. Contact him at jkaufman@dispatch.com or on Twitter @joeyrkaufman