No one expects Day to totally change the system in place since Urban Meyer took over in Columbus in 2012, but some subtle adjustments could have significant impact.
Day has been revamping the passing game since arriving as quarterbacks coach and co-offensive in 2016, and new passing game coordinator/quarterbacks coach Mike Yurcich is expected to assist in the further evolution in that area.
>>READ MORE on the offense’s outlook for spring
"The playbook is the playbook," Day said on National Signing Day. "What plays we emphasize is based on the quarterback, always has been.
"The other part of it is, who is the best 11. Does it mean there's an extra tight end, extra running back in the game. How does that fit. Each year we'll put the best guys up on the board, figure out who they are, how does that match with what the quarterback can do. What makes him special."
Day also said he is intrigued by some of the things the Oklahoma State offense did with tight ends as blockers in the running game during Yurcich’s time as Cowboys offensive coordinator.
2. How will the defense change?
Ohio State will maintain its 4-3 base, but new co-coordinator Greg Mattison figures to put his own spin on it.
The front four could be configured differently, and Mattison has hinted the linebackers will see their roles adjusted.
Fellow co-coordinator Jeff Hafley has said he wants to continue to play press man in the secondary, but there is an expectation he will bring more variety to the back end than predecessor Greg Schiano did.
That likely will involve moving to a family of coverages known as “pattern matching” that is somewhat like college basketball match-up zone.
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The nickel package could be revamped, too, but the biggest change might not involve Xs and Os.
“They're in a laboratory right now putting that all together, kind of the way two years ago with Urban, myself and Kevin Wilson,” Day said. “We were all in a room together the three of us putting together ideas, how that works. The give and the take there was really good. I think it's going to be the same way with those guys this year.”
The “Silver Bullets” defense’s fundamentals could use some sprucing up across the board after what was statistically the worst season in school history.
Co-coordinator Jeff Hafley explains his philosophy on man coverage and teaching players to look for the ball
3. How do the quarterbacks look?
Justin Fields comes from Georgia considered a five-star talent, but coaches don’t often draw firm conclusions about players until they get to work with them personally.
Fields will need to hit the ground running as far as learning the offense while the coaching staff figures out exactly what are his strengths and weaknesses.
>>RELATED: Why Fields chose Ohio State
Emphasizing the former is Day’s stated goal, but he has to evaluate what he has first.
Meanwhile, Matt Baldwin has the benefit of a year in the system but catching up to do physically after spending last year putting a high school knee injury in the rearview. He won’t give up the starting job without a fight.
4. How does the offensive line shake out?
Line coach Greg Studrawa has to replace four full-time starters, but he has four solid options to join returning starter Thayer Munford.
In December, Studrawa raved about the progress redshirt freshmen Josh Myers and Wyatt Davis were making, so they are expected to step into starting roles with Myers at center and Davis at guard, where Davis started the last two games last season after Demetrius Knox was injured.
>>RELATED: Miamisburg’s Myers preparing for major role this season
Branden Bowen, a starter at guard two years ago before suffering a broken leg that continued to bother him last season, is healthy and expected to start at guard or tackle.
Josh Alabi, the No. 3 tackle last season, is also a strong candidate to move into a starting role this spring while junior Gavin Cupp, redshirt freshmen Max Wray, Matthew Jones and Nicholas Petit-Frere and true freshman Ryan Jacoby will also push for playing time.
5. Who emerges in the defensive line room?
Coach Larry Johnson can go an amazing four-deep with scholarship players at all four spots up front, so the competition for playing time could be epic.
(This includes three five-star prospects and 10 four-stars, by the way.)
The established trio of ends Chase Young and Jonathon Cooper and tackle Robert Landers are back, but that leaves at least five spots to fill for a coach who loves to rotate heavily.
Also worth watching is if there is a philosophical shift from playing right and left ends to a heavy end and a rush end as Mattison did at Michigan, where he was also the defensive line coach.