COLUMBUS — One player does not make or break a recruiting class.

But it would be hard to overstate the importance of Ohio State getting Zach Harrison’s signature on a letter of intent Wednesday.

“Huge,” soon-to-be coach Ryan Day said. “Huge.”

Harrison, a 6-foot-5½, 243-pound defensive end from Olentangy Orange, is the top prospect in Ohio and No. 4 nationally. He also considered Michigan and Penn State. Losing him to either of those rivals would have been an unmistakable blow for a program in transition.

“Anytime you're competing — you're competing for recruits, you're competing on the field — and this was one of those ones we had to win,” Day said. “He's down the street, and so that was a big get for us.”

It was hardly inevitable. Harrison had been inscrutable throughout the recruiting process, leaving observers to read tea leaves that might not have existed. A month ago, most recruiting analysts believed that he was leaning toward Michigan.

How much Ohio State’s Nov. 24 rout of Michigan, or the impending coaching change from Urban Meyer to Day, affected Harrison's decision is a matter of speculation. What isn’t is that Day and Ohio State, with defensive line coach Larry Johnson leading the charge, worked hard to make Harrison feel comfortable with the idea of becoming a Buckeye.

“Larry, he's a legend,” Day said. “He has a legacy here, and what he's done with the defensive line, obviously, that's testimony. And so there's defensive linemen all over the country that want to come to get coached by Larry Johnson, and you can see that again in this class, and the relationships that he built are really, really important. But the way he develops the young men on the field and off the field is what's key.”

First at Penn State and now at Ohio State, Johnson has recruited and developed a succession of first-round picks, with Joey Bosa being the most recent and Nick Bosa the next.

Harrison has a chance to join that list.

“When you look at somebody who runs a 10.8 100-meter dash at his size, and the potential that he has, all you think of is the Bosas of the world and some of the top defensive ends in all of America,” Day said of Harrison’s potential.

But Harrison isn’t a finished product, and Olentangy Orange coach Zebb Schroeder alluded to the work ahead of the player just before Harrison announced his choice during a closed ceremony at the school. Harrison will enroll at Ohio State next month.

“As the recruiting process now ends, the college-football player process begins in a couple weeks,” Schroeder said. “These guys have been recruiting you and showing you all the love. Remember that when you get there in January, it’s about business, and the business is about becoming the best student-athlete you can become for that institution. It’s been fun, but now the real fun and the real grind starts.”

Day had felt good about Ohio State’s chances after he visited the Harrison family. But in recruiting, nothing is a given.

“I think there was a connection made there, and obviously the connection that Larry had with the family was really, really important,” Day said. “I believe that the family trusted that we were going to take care of their son when they came to Ohio State.”