Ohio State’s new coach, Ryan Day, has been described as an “elite” coach and an “innovative thinker” who has helped build the Buckeyes into one of the most explosive passing offenses this season led by Heisman Trophy finalist, quarterback Dwayne Haskins.

But he also is a quick study.

The 39-year-old Day succeeds Urban Meyer, 54, who on Tuesday announced his retirement from coaching. Meyer won three national championships during his coaching career, including one with Ohio State, which he coached for seven seasons.

Day, who was officially introduced as the Buckeyes’ 25th head coach during the Tuesday news conference, is from New Hampshire but said he was indoctrinated quickly in what’s important at Ohio State.

“No. 1, win the rivalry game,” Day said, referring to Michigan. “And No. 2, win every game after that.”

He has been co-offensive coordinator and quarterbacks coach the last two seasons and called the plays this fall. Day will take over as Ohio State’s head coach on Jan. 2, the day after the Buckeyes’ Rose Bowl against Washington. It has been 72 years since Ohio State has hired a coach with no head coaching experience.

In what amounted to a head-coaching dress rehearsal, Day went 3-0 to start this season, including a victory over then-No. 15 TCU on the road, as interim head coach while Meyer was suspended. Ohio State finished the season 12-1, including victories over Michigan in the regular-season finale and a Big Ten championship after defeating Northwestern.

“Ryan Day is elite,” Meyer said Tuesday, echoing the comment he made several times this fall.

Day said the things transpired “really fast” the previous two days after Meyer had made his decision. Ohio State athletic director Gene Smith said he considered a national search, but he admired how Day conducted himself during what amounted to a three-game head-coaching audition.

“It’s rare you have the opportunity to create a succession plan where you have the right person in place,” Smith said. “We recognized the talent Ryan Day had early.”

Smith said he began spending considerable time meeting with Day during the summer. He also continued a tradition of meeting with Meyer every Sunday after games, and they began discussion a possible head coaching transition.

“We had deep conversations about that,” Smith said. “While we were having those conversations I was looking at candidates across the country and trying to decide if I was going to go national search. When I thought about those potential candidates — and some of them are very good and some of them I know -- I felt more comfortable coming back to Ryan Day.

“Our program does not need disruption. It does not need to blow up and have people come in and try to adapt to our standards of operation and try and change the infrastructure we put in place for the student-athlete. We had a talented and gifted guy that many others wanted to interview and potentially hire.”

Day worked on Meyer’s staff at Florida and is considered a protegee of Chip Kelly, now at UCLA. He was pegged as a rising star in the coaching profession and reportedly turned down significant job opportunities in the offseason, as Mississippi State head coach and Tennessee Titans’ offensive coordinator. His loyalty to Ohio State was rewarded with a new contract — he became the program’s first assistant to make $1 million.

He has signed a five-year contract worth $4.5 million a year, according to the Columbus Dispatch.

“Very humble to be taking over for coach Meyer,” Day said. “The footprint that he’s left here and infrastructure is strong. Knowing that and being here for two years and seeing exactly how it’s been done gives me great confidence.”

When Meyer became head coach at Bowling Green, he was 36. He said he would not have been prepared to take over at Ohio State at such a young age. Day, though, he said, is more than prepared, even at 39.

“He’s very unique to be able to handle that,” Meyer said.

Day doesn’t plan any major shake-ups.

“Any time there’s a change in leadership, there’s a different personality, there’s a different style, a different demeanor,” he said. “We share so much in common that there’s going to be a lot that carries over. Most of what coach has built here is going to stay. As we go along there’s going to be some changes in terms of the way we do certain things. Our beliefs are strong.”

This season under his guidance, Haskins has had a record-breaking season at Ohio State. He is No. 1 nationally in passing with 4,580 yards and is No. 2 in passing per game (352.3 yards average). The Buckeyes ranked second nationally in offense, averaging 548.8 yards, and second in passing (373.0).

“He is an innovative thinker,” ESPN college football analyst Kirk Herbstreit, a former OSU quarterback, said Tuesday on the network referring to Day.

Former Ohio State quarterback Cardale Jones praised Day in a Twitter post on Tuesday.

“Ryan Day is the best thing to happen to the Ohio State offense since the absence of Tom Herman,” Jones wrote. “Developing players & calling plays that benefit their skill sets.”

There will be some continuity on the staff in the transition from Meyer to Day. Among those reportedly staying with the Buckeyes are strength coach Mickey Marotti, and head of football operations Brian Voltolini, Ryan Stamper (off-field player development) and Mark Pantoni (recruiting).

Day, who coached quarterbacks in the NFL for Kelly at Philadelphia in 2015 and San Francisco in 2016 before joining Ohio State’s staff, was co-offensive coordinator with Kevin Wilson, who had most recently been Indiana’s head coach.

He had worked for Meyer in 2005 as a graduate assistant at Florida.

Day knows something about coaching quarterbacks because that’s the position he played in high school and college. He was the New Hampshire Gatorade Player of the Year at Manchester Central High and was three-year starting quarterback at New Hampshire.

He launched his coaching career in 2002 at his alma mater working with the tight ends. Day quickly moved up the coaching ranks. He was offensive coordinator at Temple in 2012 and then at Boston College, 2013-2014.

Twitter: @chengelis