Chase Daniel concocted an idea this summer, motivated by inspiration and spite. To capitalize on the NFL's new plans to review pass interference, the Chicago Bears' backup quarterback proposed a twist: Throw a Hail Mary pass in the first quarter of a game.

The ball would fly into the end zone amid the usual jostling, grabbing and pulling by defenders on such plays. Assuming the ball fell incomplete, as most Hail Marys do, Daniel suggested that Bears coach Matt Nagy immediately throw his challenge flag. The NFL replay command center would have no choice but to either call or uphold pass interference on the defense, Daniel reasoned, and give the Bears an easy -- and early -- 50 yards.

"Why not?" Daniel said after a recent Bears training camp practice. "Everybody's grabbing and holding and they rarely get intercepted. It's a jump ball for the receiver. If you get pulled, it's a big gain and you're on your way to an easy touchdown. There are new rules every year, and every year there are new ways around them. My mind is going crazy with all the things we've talked to Nagy about."

Yes, there are a few holes in Daniel's idea, but his enthusiasm illuminates the largely untold but significant downwind impact of NFL rule changes. While many observers are fretting the expansion of replay, coaches have spent the spring and summer devising ways to manipulate it for competitive advantage. The first step, as the preseason begins in earnest Thursday, will be to test the system for clues on how it will operate in the regular season.

A preseason of experimentation

Coaches surveyed this month indicated they will use their challenge flags liberally in preseason games, hoping to compile a collective library of the type of contact that would -- or wouldn't -- prompt senior vice president of officiating Al Riveron to overturn a judgment call on the field. Retired referee John Parry, now an ESPN rules analyst, estimated there will be as many as 60 such challenges in the course of 65 games. For context, NFL coaches challenged 156 total calls in 256 regular-season games last season.

"I just want to make sure that I understand, and that we understand as coaches, exactly what they're going to overturn or not," Minnesota Vikings coach Mike Zimmer said. "I'm under the understanding that they're not going to put many flags on the field, and they're not going to pick many up. But if they start slowing that camera down to look at it frame-by-frame? Who knows. That's why, in the preseason, you might as well use those challenges and see what happens."

Indeed, the leaguewide expectation is that Riveron will use an exceptionally high standard to change a call, reserving his reversals for only the most egregious mistakes. Green Bay Packers president Mark Murphy, a member of the competition committee, said, "We really want the standard to be pretty high" to maintain game flow and also mitigate against differences in camera angles for various games.

Losing a challenge requires a team to forfeit a timeout, so during the regular season, Zimmer and other coaches won't want to risk a timeout for any challenge that falls short of that standard.

Underlying opportunities

At least some coaches, however, hope to identify hidden opportunities to use the rule to their advantage. Daniel's idea is one. But officials have historically been unwilling to call pass interference on Hail Mary plays. And most Hail Marys, of course, will fall under the jurisdiction of on-site replay officials -- who take over responsibility for challenging calls during the final two minutes of each half and overtime -- rather than be subject to a coach's challenge.

Even so, running a Hail Mary-type pass in the first quarter would put Riveron in a difficult spot. He would be forced either to overturn a no-call or, to maintain the Hail Mary standard, allow a potentially egregious level of contact to go unaddressed.

There are other possibilities as well. Former NFL referee and current NBC rules analyst Terry McAulay suggested this spring that coaches should challenge whether offensive linemen commit offensive pass interference when blocking downfield on run-pass option plays, an illegal act that rarely is flagged. And then there is the potential for teams to use plays designed to draw the red flag from opposing coaches, in hopes of draining that team's challenges early in a game and opening the door for more physical defensive play thereafter.

If you think any of this is far-fetched, you're underestimating the lengths to which NFL coaches will go to gain an advantage. It is not unusual, for instance, to see smart playcallers design route combinations that incorporate officiating positions and assignments. If timed correctly, those plays allow a receiver to run downfield without an official seeing him.

"There is something to be said for that," Parry said. "It's very much apparent now with Next Gen Stats and NFL analytics. Each team has a coaching staff where their job is to design plays that challenge their opponents, which is the whole premise of the game, and in return, plays that also challenge the on-field officials. Coaches are bright and understand which official is assigned to which player and when. And there might be a situation where replay is used strategically as well. That's just a very true statement."

Most of it will go unnoticed by the viewing public, and none of the coaches I spoke with wanted to broach the subject in any detail. Nagy said he is spending training camp off-days with a small group of game management advisers, planning for every potentially challengeable call imaginable. The most difficult decisions, he said, will be plays that occur before their impact on the outcome of a game is clear.

"To keep it simple," Nagy said, "you kind of think, 'First half, no, second half, yes.' And you know you're protected on scoring plays by automatic reviews. The ones that will be hard are the ones where it's like a 60-yard play and the guy gets tackled at the 1-yard line in the first quarter. If you're on defense, you'd love to get that play called back. That's a big one. But there's going to be gray there. Are they really going to overturn it? That's where you have to make a tough decision."

Deciding when to chance it

Public discussion of challenges has long outpaced coaches' actual comfort level in using them. Hoarding timeouts has always outweighed the potential loss of a timeout. In the 20 seasons since replay was re-instituted in 1999, coaches have challenged 3,968 calls -- an average of less than one per game for both coaches combined. And there are only nine instances since 2001 of a coach using his maximum of three challenges in one game, according to ESPN Stats & Information.

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Parry predicted that some coaches will shift their thinking and view challenges the way basketball coaches think of timeouts. You might as well use them, the theory goes, because there are no rewards for having them in your pocket at the end of a game. For the first time in the NFL, challenges could be a weapon rather than just an emergency tool.

No coach would acknowledge such a shift, and some, including Packers first-year coach Matt LaFleur, don't seem ready to jump into the nuance of challenge strategy.

"You always want to be selective and weigh the cost benefit," he said. "Really, how confident are you that something is going to be overturned? And those timeouts at the end of a game are still really valuable. So I see it a little bit different than the basketball analogy. Maybe you'll be more aggressive when it's close than you would have been on something else, but that's why this preseason is going to be so important, to get a feel for how it's going to get ruled."

There was one challenge in the Hall of Fame game. Denver Broncos coach Vic Fangio threw his flag in the second quarter after the Atlanta Falcons drew a 43-yard defensive pass interference penalty against cornerback Linden Stephens. The replay showed only moderate contact by Stephens against Falcons receiver Russell Gage. But Riveron upheld the call, saying later that there was "no clear and obvious visual evidence" to merit reversing it.

"First replay review of the year for defensive pass interference last night. No clear and obvious visual evidence to reverse the on-field ruling of DPI. Therefore, the call stands." - AL pic.twitter.com/d6tpA2pXp8 — NFL Officiating (@NFLOfficiating) August 2, 2019

Those who feared the intrusion of a game-altering rule change could relax for one week. But beginning with the 11-game Thursday night slate to open Week 1 of the preseason, Riveron will face the pressures of multiple games and perhaps concurrent challenges.

And if Chase Daniel has anything to say about it, he could see a Hail Mary or two as well. Welcome (back) to the world of NFL rule manipulation. It's always lurking.