Mel Kiper Jr. says defensive end Nick Bosa's withdrawal from Ohio State is a "business decision" because he is preparing to be a top NFL draft pick. (1:47)

Ohio State defensive end Nick Bosa has withdrawn from school to focus on his rehabilitation of an injured core muscle, the Buckeyes announced Tuesday. The All-American will now presumably turn his attention to the 2019 NFL draft.

"I was hopeful that Nick would be able to return to play again for us," Ohio State coach Urban Meyer said in a statement. "I know this was an extremely difficult and emotional decision for Nick and his family, and I wish him well as he moves on to get himself 100 percent healthy and ready for his next chapter. I want to thank Nick for the remarkable efforts he gave for this program. He is a first-class young man who we have been honored to coach."

During Tuesday's Big Ten conference call, Meyer described meeting with the Bosa family.

"It was very emotional," he said. "We love Nick. The Bosa family has been awesome for Ohio State and the program. Nick is a first-class guy."

Bosa, a junior, injured a core muscle in the third quarter of a 40-28 win over TCU on Sept. 15, had surgery to repair the injury on Sept. 20 and has since been recovering. The reigning Big Ten Defensive Lineman of the Year had not been cleared for team activities and was ruled out for the upcoming game against Purdue.

Hope remained among Ohio State officials that Bosa could return to see meaningful playing time in the regular season, but John Bosa, Nick's father, told Sports Illustrated that that hope died a while back within the Bosa family.

"The realistic time frame is 12 weeks," John, told SI.com Tuesday. "Twelve weeks brings us into December."

The College Football Playoff semifinals are Dec. 29. To John Bosa, that's not enough time for his son to recover.

"There's time frames for injuries, and then time frames for an elite pass-rusher. It's not about rehabbing so you can be back on the used car lot or be a mechanic," he told SI.com.

"When is he able to be safe and play at the same level? When you look at the preparation he goes through in preseason, that's not a realistic time frame for it to be safe. It's just not."

Through just three games of the season, Bosa had four sacks and six tackles for loss and was leading the team in tackles at the time of the injury.

Nick is the younger brother of Los Angeles Chargers defensive end Joey Bosa, who also starred at Ohio State and was selected third overall in the 2016 NFL draft. Nick Bosa is the No. 1 prospect on Mel Kiper Jr.'s latest Big Board rankings of the top players for the 2019 draft.

Bosa won't be re-evaluated until November.

The injury is not expected to impact Bosa's draft status, and the decision to withdraw from school to focus on his rehab reduces the risk of aggravating the injury and potentially hurting his draft stock.

Asked about Bosa, as well as future first-round pick Denzel Ward skipping Ohio State's bowl game last year, Meyer praised both and said: "I certainly understand and we support [the players]. It's just something you've got to deal with and move forward, just like early entries in the draft. It just happens."

Meyer said Jonathon Cooper, Chase Young and Jashon Cornell will be the team's primary defensive ends, and that Tyreke Smith could take on a bigger role with more experience.

Meyer hadn't addressed Bosa's departure with the team yet.

"This just happened. We're still debating on how to do it," he said.