Rece Davis reveals the top six in this week's College Football Playoff rankings, with Ohio State remaining at No. 1 and Oklahoma jumping to the No. 6 spot. (1:28)

After Ohio State beat Michigan in the final game of the regular season, head coach Ryan Day acknowledged the pressure he felt coaching in the rivalry game: that he was following in the footsteps of Urban Meyer, that he would be judged on the outcome and that the magnitude of winning that final game and completing an undefeated season would have even bigger ramifications.

In his first season as head coach, Day and his staff have guided Ohio State to a 12-0 record with a chance at a Big Ten Championship and a berth in the College Football Playoff, all while erasing any concerns that there would be an adjustment period post-Meyer.

"To say there's not stress coming into a game like this would be a lie. There's so much riding on a game like this," Day said. "And you understand, and you feel the weight of everybody involved with it. And a win like this right now, it's a relief. It is."

It didn't happen without some growing pains and lessons learned, but through smart offseason hires, player development, attention to detail and some outstanding recruiting, Day is already meeting the lofty expectations set for him.

Understanding just how difficult it is to go 12-0 in today's college football landscape and how much can change in a matter of weeks, Day has been effusive in his praise of his players and assistant coaches, who have all come together to produce an impressively productive season.

Those coaches -- and their development of the players -- are where this 12-0 season started, when Day made changes to the staff to fit his personality and help fill the voids to improve the team. Day instantly made the offense better when he was hired as co-offensive coordinator before the 2017 season, and he was instrumental in guiding quarterback Dwayne Haskins to his record-setting 50-touchdown season in 2018.

Integral once again to this offense in 2019, Day brought in Mike Yurcich as passing game coordinator and quarterbacks coach. Under Day and Yurcich, first-year starter Justin Fields has the second-most touchdown passes in a season in Ohio State history, behind only Haskins' total.

Fields initially competed with Matthew Baldwin for the starting job, but Baldwin transferred to TCU in April, cementing Fields' spot as the starting quarterback and resting the fate of the offense on his shoulders.

A former five-star and No. 1 recruit, Fields showed his talent and ability in high school but didn't get a chance to show what he is capable of in his short time at Georgia. The question of how Fields would adjust to Ohio State's offense was quickly erased as he threw for 880 yards and 13 touchdowns while rushing for 150 yards and six touchdowns in his first four games. In that time, Fields threw touchdowns to eight players, erasing any doubts about what this offense could be.

The strength of schedule through those first four games was on the weak side, but the Buckeyes still impressed in outscoring their first four opponents 214-36.

So many playmakers on the outside, combined with Fields ability to pass and run, made the offense difficult to stop. But what made this offense so effective and balanced was the consistency of running back J.K. Dobbins.

The third-year back became Ohio State's second all-time career rusher behind Archie Griffin, passing Ezekiel Elliott. He currently has 4,113 rushing yards after running for 1,446 yards and 15 touchdowns this season.

Many thought Dobbins would be tested against Michigan State's defense, which prior to that game against the Buckeyes held opponents to 55.8 yards rushing per game, fifth in the country.

All Dobbins did in that game was carry the ball 24 times for 172 yards and one touchdown. Backup Master Teague had 90 yards rushing, and Fields contributed 61 yards and a touchdown to give the Buckeyes 323 total rushing yards in a 34-10 win.

The offense relied heavily on the run game once more against Wisconsin, which had the No. 1-ranked rush defense coming into that game. Through the first seven games of the season, Wisconsin held opponents to 58.4 yards rushing per game and allowed only two rushing touchdowns.

Ohio State ran 50 times for 264 yards and three touchdowns against the Badgers. Dobbins had 163 yards and two touchdowns, and Fields had a touchdown as well in a dominant 38-7 win.

The offense hasn't slowed all season and has averaged an FBS-best 49.17 points per game.

Ohio State coach Ryan Day celebrates the victory over Michigan with two key defensive players from the 2017 recruiting class, Baron Browning, left, and Chase Young. Gregory Shamus/Getty Images

Those numbers are impressive, but the most dramatic difference in this team has come on defense, where Day added co-defensive coordinators Jeff Hafley and Greg Mattison, as well as linebackers coach Al Washington.

The Ohio State defense ranked 72nd in yards allowed per game in 2018, giving up 403.4. That stat has improved drastically in 2019, as the Buckeyes lead all FBS teams in allowing just 232.3 yards per game.

The unit has gone from 56th in rush yards allowed per game in 2018 to fourth this season and from 86th in pass yards allowed per game to second this season. Another area in which the team is really seeing a difference is explosive plays, having cut the number of plays going for 20-plus yards from 67 in 2018 to 33 so far in 2019.

That effort has been led by marked improvements in the secondary and has seen cornerback Jeff Okudah separate himself as one of the best defensive backs in the country.

"From the first time we had [our defensive players], everything was about fundamentals and technique," Hafley said. "It was trying to build a scheme where they could line up and maximize their ability by playing fast, knowing what they're doing. And that was the whole key. We wanted a clear understanding of the defense. We wanted a clear understanding of how hard we had to play and how tough we had to be, and we kind of ran with it from there. We've tweaked along the way, but we've never turned back from the philosophy we started with."

That philosophy and attention to detail have created a well-balanced team with an FBS-best point differential of 457 this season. Ohio State has been a well-oiled machine that has had little trouble getting through its opponents.

It hasn't hurt, either, that the defensive line has been anchored by arguably the best player in college football, defensive end Chase Young, who in 10 games this season leads all NCAA players in sacks with 16.5. Young was suspended for two games, against Maryland and Rutgers, for taking a loan from a family friend, but he has shown up in big games all season, with four sacks against Wisconsin and three against Penn State.

Young was part of the Buckeyes' outstanding 2017 recruiting class, which ranked No. 2 in the country and has been an integral part of this season's success. In all, 12 of the 21 prospects Ohio State signed in the 2017 class have been important contributors this season.

The top-four ranked recruits in that class -- defensive backs Shaun Wade and Okudah, linebacker Baron Browning and Young -- all have had an impact this season. Dobbins, offensive linemen Josh Myers, Wyatt Davis and Thayer Munford, defensive back Amir Riep, defensive lineman Haskell Garrett and linebackers Brendon White and Pete Werner also were part of that class.

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The 2017 recruiting class was important, but one of the biggest recruiting wins for Day and his staff came when Fields decided to transfer from Georgia.

Fields had the skill set and ability to match Day's offense, and the timing was perfect. Haskins had declared for the NFL draft, and Joe Burrow transferred to LSU before the 2018 season, leaving Ohio State with no real answer at quarterback.

"I can't sit here and say there was one plan," Day said. "Once Dwayne decided to enter the draft, everything went into a tailspin, really, to be honest with you. That was a very tough situation. You're talking about somebody who had three years left. He comes for one year and leaves. That affects recruiting. It's obviously a very sensitive position."

The intuition that Fields would be a great fit was spot-on. Day, Yurcich and Fields hit the ground running. Fields has thrown 37 touchdowns with only one interception and has garnered Heisman talk, with many, including his coach, thinking he should be at the award ceremony in New York City.

But first things first. Day has kept the players and himself focused on the task at hand and the team in front of them. The Buckeyes have not looked beyond the challenge immediately ahead, and the result has been their first 12-0 regular season since 2013.

After the Buckeyes beat Michigan to finish their perfect regular season, Day understood what it meant in that moment and what it could mean for the future. But he won't allow himself to look too far into that future.

"I think we've done a good job of staying one week at a time and staying one day at a time," he said, "because when you start to think too far ahead, you get yourself jammed up."