COLUMBUS, Ohio — Marvin Harrison Jr. has been a problem for every defense he’s faced, and nobody knows that more than the defensive coordinator who sees him in practice every day.

Jim Knowles arrived at Ohio State in December 2021. He can’t remember which Harrison play stood out the most so early, but it took him just one practice at Ohio State to realize that Harrison was different.

“I just knew we were going to have a tough time,” Knowles said.

Every defense Ohio State meets has the same goal of containing No. 18. But that’s easier said than done. In the past two seasons, Harrison has 139 catches for 2,356 yards and 27 touchdowns. That doesn’t even include the three touchdowns he had against Utah in the Rose Bowl to cap his freshman 2021 season, his breakout performance.

Since then, the son of Indianapolis Colts legend Marvin Harrison and the 14th-ranked receiver in the 2021 recruiting class has developed into the best receiver in the country — with an argument for the best player, period. Last Saturday’s win against Minnesota was likely Harrison’s last game in Ohio Stadium, assuming he turns pro early as a projected top-10 NFL Draft pick.

But first, this Saturday will be as big of a game as Harrison has played in when No. 2 Ohio State visits No. 3 Michigan in a battle of 11-0 teams and one of the most consequential matchups in the history of the storied rivalry. It’s Harrison’s chance for a signature moment to add to his Heisman Trophy campaign.

When Harrison leaves Ohio State, he’ll go down as one of the best players in the history of the program, regardless of what happens in the Heisman race. So what makes Harrison so difficult to stop? The Athletic surveyed a handful of people most familiar with Harrison’s on-field exploits for their perspective and favorite memories of the standout wide receiver.

Jim Knowles

Who he is: Ohio State’s defensive coordinator for the past two seasons, Knowles has had Harrison as the ultimate measuring stick for his secondary, which gave up too many big plays last year but has developed into one of the best in the country in 2023.

How he views Harrison: Harrison credits Ohio State with helping him develop all of his skills, allowing him to play in a variety of positions and ways. The Buckeyes don’t use Harrison just as an outside vertical threat. They use him in the slot, on shallow crosses and even running the ball, like he did with a 19-yard touchdown against Michigan State earlier this month. His expertise in running a diverse route tree makes him a matchup nightmare.

“That whole thing is difficult for me to handle in practice,” Knowles said. “I remember one time in practice we had a bracket on him, two guys, and he went through both of them and just caught the ball. I was like, ‘How can that happen? We have two guys on him.’ Well, that’s Marv. He just went over both of them and caught it.

“It’s extremely challenging for a defense, and then the creativity that (Ryan Day) has and all those guys do a great job of utilizing that.”

Kyle McCord

Who he is: The Ohio State quarterback has been teammates with Harrison since their sophomore year at St. Joseph’s Prep in Philadelphia. Now, Harrison has been his go-to weapon in McCord’s first year as the Buckeyes’ starter, leading the Big Ten in receiving yards while McCord ranks second in the league in passing efficiency.

How he views Harrison: Before McCord and Harrison pursued a College Football Playoff national championship together, they were part of the same 2021 Ohio State recruiting class after winning three consecutive Pennsylvania Class 6A state championships in high school.

It didn’t take long for a connection to form.

“My favorite moment with him was our sophomore year of high school,” McCord said. “He went to our rival school our freshman year, La Salle College High School. We played La Salle our sophomore year and it was sold out. The whole student section is chanting ‘overrated’ at him, and then he came out and had more than 100 yards or something and two touchdowns.

“That was kind of like his coming-out game where he let everybody know he was legit. Seeing him do that on that stage, in front of his old team, that’s when I knew he was special.”

McCord and Harrison have just about grown up together. For McCord, it’s been special watching one of his closest friends turn into a top NFL Draft prospect.

“It’s cliche, but I’m not surprised with what he’s done at all,” McCord said. “When you mix his physical gifts, being 6-foot-4 and being able to run routes like he does, just as physical he is, and you pair that with his mind and his work ethic, the sky’s the limit for him. Seeing him being projected to go No. 1 in the draft, that’s not surprising to me knowing the type of player he is and the type of person he is off the field. I think it’s been a cool journey and one I will cherish.”

Ryne Morrison

Who he is: Morrison was Harrison’s high school wide receivers coach at St. Joseph’s Prep.

How he views Harrison: In 2019, their junior year at St. Joe’s Prep, McCord was injured, forcing the team to move a receiver to quarterback — and thus changing what the offense looked like. Still, Harrison took over when Prep needed him to.

“Marvin’s targets were diminished, but we had our backs against the wall in the semifinals against (Pittsburgh) Central Catholic,” Morrison said. “We had the ball inside our own 15-yard-line. We only threw eight or nine times, and a lot of those were swing screen stuff — we didn’t ask our quarterback to throw across the line of scrimmage. It was a 14- or 15-play drive, and we scored at the buzzer, and at some point during that drive Marvin had a third-and-12 or third-and-15 or something like that. A catch over the middle, a dig route, and Marv came up gimpy, got his ankle rolled up. He came out for one play, taped him up real quick, threw him back out.

“He got back in, and as legend has it we got the ball inside the 10-yard-line, fail on first, fail on second, fail on third. On fourth down, we had a crazy broken play, it turned into a scramble drill and Malik (Cooper) ended up just throwing it up for grabs and there were six or seven bodies there and all of a sudden No. 8 just goes sky high over everybody and toe taps in the end zone. It’s the best high school catch I’ve ever seen. The most impactful single play of his career, just to keep the season alive. … It was really special. It will be burned in all of our minds here.”

Off the field, Morrison had a funny story about Harrison that showed off his elite athleticism at a young age when weather caused an outdoor practice to be moved inside to a basketball court during Harrison’s sophomore year playoff run.

“It was a Wednesday or Thursday practice, a tune-up before the game,” Morrison said. “Not practicing full speed was good for us. We had a senior receiver, Johnny Freeman, he saw a basketball laying around. As we were walking off, he picked up the ball and went to look like he’s going to dunk and I said, ‘Don’t even think about it.’ He said, ‘Why?’ I said, ‘No, we have a game in 48 hours. Once the season is over, go for it.’ He dropped the ball with this dejected look on his face.

“At the same time, we both turned around and Marvin has his shoulder pads on still and he’s on the other side of the court. He picks up a ball and windmill dunks it, with his shoulder pads on, he’s like looking at the rim. Johnny is like, ‘Coach, what the hell?’ I said, ‘I don’t know what to tell you.’ The sheer shock value and irony, it was a small moment that I have that was funny. You can appreciate his raw athleticism. I was like, ‘There’s something different about this kid.’”

Brian Hartline

Who he is: Ohio State’s offensive coordinator and wide receivers coach, Hartline is known as one of the best recruiters in the country. The former Buckeye recruited Harrison to Ohio State.

How he views Harrison: Hartline recalled moments in practice where he’d catch himself talking to himself about Harrison saying, “Yep, there it is.” Hartline would challenge Harrison in a particular area, and it wouldn’t take long for it to translate on the field.

“Early on, the conversations I would have with him, challenging him and the ability to hone in on something and see if he can apply it and then he does, it’s that,” Hartline said. “It’s also when I challenge him mentally or I see a chink in the armor or he’s doubting himself in any type of way, I’ve attacked that doubt, or I try to, and I see if he takes it and runs with it and he does.

“All I’m saying is that every time he’s been challenged or we have a good conversation, he really works to apply it. That’s a special talent of its own. There’s been multiple occurrences, I can’t give you the exact scenario, but they are daily. When he was younger it was, ‘Oh yeah, he has a real chance.’ And now it’s daily, as I have conversations with him, it’s a reconfirmation.”

Though everybody around the country raves about Harrison when he makes eye-popping plays, Hartline said the impressive thing he’s seen with Harrison is his ability to make the flashy catch while also staying consistent.

“I don’t want to minimize playmaking — everybody can make the plays, but it’s the consistency of how often,” Hartline said. “That’s what we’re chasing. The crazy play is just as important as the non-crazy play. … People forget about the crazy play if you don’t make the consistent play. People miss that sometimes, but Marv doesn’t.”

Perry Eliano

Who he is: Eliano arrived at Ohio State as the safeties coach last season after a two-year stint as the cornerbacks coach at Cincinnati, where he coached All-Americans Sauce Gardner and Coby Bryant.

How he views Harrison: Like Knowles, he has firsthand knowledge of what it’s like to try to coach against Harrison every day in practice. He also sees it when he arrives for work every day at the Woody Hayes Athletic Center.

“All you gotta do is come in the mornings, afternoons, summer, the weekends and Marvin Harrison Jr. is in the Woody working,” Eliano said. “That’s when I knew. I’ve been around a guy that could just dominate practice or a game when I coached Sauce (Gardner), and he’s that. He affects the game directly, but everything you see on the field is not shocking because he is in here working and he’s the most gracious and humble individual that I’ve ever been around. He works summer, fall, spring, weekends, he’s in here working.”

Asked if Eliano remembered the catch Knowles was referring to, when Harrison just went through two Ohio State defenders in practice, he said he did.

“That reminded me of when he ran right by, I want to say it was Western Kentucky or somebody, trying to bracket him and he just ran right by both defensive backs like they were standing still,” Eliano said. “There’s not one moment, because there’s several moments I’ve seen when I’m like, ‘Wow, this dude is a problem.’ People consistently cover him one-on-one and I’m like, ‘I see this dude every day. You better know where he’s at.’ But like I said, I knew when I first got here, over a period of time, it’s his work ethic and how serious he is about his business.

“It’s consistent. No matter if he had three touchdowns or just one touchdown, he’s out here working.”

Ryan Day

Who he is: Ohio State’s head coach since 2019, Day has had a play-caller’s best friend in Harrison lining up at receiver.

How he views Harrison: “It’s when I come into the building and he’s already on the JUGS machine catching,” Day said. “That’s what I will remember the most. I mean, his first big game was the Rose Bowl and that’s where he kind of came onto the scene. Then the big plays he’s made and his work ethic.

“He’s made a tremendous impact on the entire program and he’s going to leave something behind. I think it’s his work ethic, that’s the big part of it.”