Lions' offense dunking defense into 'deep end of the pool.' That's a good thing.

More than ever, each snap in the NFL is a game of chess: which side of the ball can outwit the other? Lions safeties coach Jim O'Neil felt the pieces on the offensive side of the board start to move more dynamically toward the end of his tenure with the Raiders in 2020, when pre-snap motion "really started to amp up." When O'Neil returned to the NFL four years later with the Lions after a couple seasons in the college ranks, "it was like, every play," he said.

"That's the whole (Kyle) Shanahan influence, the (Sean) McVay influence. They're forcing guys into positions that they're not normally in, like nickels in the box playing linebacker, and they're forcing communication amongst the defense, which makes it harder on us," O'Neil said Wednesday before the Lions' final practice of the spring. "But, with Drew (Petzing), we get it before every play, which is great. We're seeing who can handle it and who cannot."

Those who can handle it are the veterans in the middle of Detroit's defense, from linebacker Jack Campbell to the safeties in the back like Chuck Clark, who's become a fast favorite of the coaching staff. O'Neil refers to them as "pre-snap erasers." Their ability to anticipate and communicate solves problems for the defense before they happen, which allows coordinator Kelvin Sheppard to go into every play with multiple calls, said O'Neil, based on what the offense might be showing.

Every NFL defense has leaders like this -- and Detroit's defense has the added benefit of bringing back its entire coaching staff from last season. What the Lions appear to have again is an offense that's forcing their defense to think on its feet, instead of getting stuck in its ways.

"That is huge in today's football game," said O'Neil. "You can't just single play call, line up and play, or, 'Hey, my eyes are here.' There are multiple levels to every call, and there are multiple things happening before the ball is even snapped."

Problem-solving, on both sides of the ball, was at the crux of what the Lions wanted to accomplish this spring. Campbell said multiple times that they were doing much more of it than they were at this time last year, when they were breaking in two new coordinators. The aim was to put the offense and defense in frequent conflict, to sharpen how both sides react.

They achieved this on offense by reducing the playbook for now, but adding a level of nuance to their core plays. It harkens back to former offensive coordinator Ben Johnson's mantra of making the same plays look different, and different plays look the same. Or in the ever-descriptive words of Dan Campbell, same girl, different skirt.

"A lot of it is, what are the things you really feel like you can hang your hat on and we already know our guys do well? We're not going to go away from those, so let's trim it down a little bit in that regard. We're doing a lot of the same things, but man, there's so much (that's) different: same girl, different skirt. It's the shifts, the motions, the turbos, the stacks, the stack inverted, and so the presentation for the defense is different. You make them have to talk, communicate, adjust on the run, and it's just enough sometimes where you gotta be disciplined on defense. You're trying to stress those guys, so that's what the uptick has been: OK, the playbook is kind of reduced right now, but we've done a lot more bells and whistles with it, which is good."

The Lions, per Sharp Football Analysis, used pre-snap motion on 52.2 percent of their plays last year, which ranked in the middle of the NFL. The Bears ranked sixth under Johnson at 60.6 percent. (The Cardinals ranked toward the bottom of the league under Petzing, but that was a much differently-designed offense than the one he's inherited in Detroit.)

Lions passing game specialist David Shaw, who was hired last year with former OC John Morton and stayed on board after Morton's dismissal, described Petzing's approach this spring as: "Trim down a little bit the things that we carry and be better at the things that we do well."

"So, we can change formations, change personnel groupings, stay in the core, keep Jared Goff in his comfort zone, keep our offensive line in their comfort zone, and go out there and just play great football," said Shaw. "It's really cutting down what we do and being better at it."

The players, by the way, have felt it. Second-year receiver Isaac TeSlaa said this week that "the biggest thing from last year to this year" is that "we’re trying to nail the basics before we start adding on stuff. I felt like there were times last year where we were thrown a lot and we had to sift through it and figure it out. This year we’ve done a good job of mastering the basic things, especially during this period where we can really harp on those things."

Maybe more importantly, the defensive players have felt it. The Lions are going to light up the scoreboard by virtue of their personnel. Their former OC was stripped of play-calling duties in the middle of last season, then fired at the end of the year after they piled up the fourth most points in the NFL.

It's their defense that will determine whether they sink or swim against top competition. And senior defensive assistant David Corrao, who's been with the Lions for nine years, said the offense is pushing them into "the deep end of the pool right out of the gate."

"Drew's doing an outstanding job," said Corrao. "He is putting pressure on us every day with shifts, motions, new alignments, new plays, that it's already putting us into the mode of, this is what we're going to see from these advanced NFL offenses."

We already know Sheppard plans to diversify his defense this season by playing more nickel, and less base. The Lions deployed sub-packages at the lowest rate in the NFL last season. The operation broke down when injuries thinned out the secondary. It was a rigid unit by year's end. The vision this year is to become more flexible before the snap, and more fluid after it.

It's not enough for each defensive player to know his assignment, alignment and reads on each play, Corrao explained. He also has to be prepared to come up with answers to pop questions, in concert with the rest of the unit: "No matter what the offense does, you should have a reaction already in place."

"That's where Drew is challenging us ... This is the NFL. The offense isn't just going to line up and show us what they're doing," said Corrao. "We have to ingrain in our players to anticipate when things are going to move, when things are going to change and the more we can do that, the better off we'll be in the long run."