The lasting image of an otherwise successful 2018 NFL season was of the missed pass-interference call in the NFC championship game that helped send the Los Angeles Rams, rather than the New Orleans Saints, to the Super Bowl. The officiating blunder hung over the league’s marquee matchup and took some of the luster off a season of captivating play and recovering TV ratings — and it led franchise owners to take the step of making interference calls and non-calls reviewable with instant replay for the 2019 season.

So, all will be well, right? The NFL can only hope so. While there now exists the safety net of instant replay to, presumably, prevent an officiating gaffe like the one in Rams-Saints from deciding a game, league leaders must cross their fingers that any unintended consequences of the replay change don’t result in more harm than good.

“I’m a glass-half-full guy,” former NFL referee John Parry said. “I hope it works. I really do. Time will tell. There are going to be plays where we all agree [whether pass interference should be called], but there are going to be some where we don’t all agree.”

The new replay system was in effect for last week’s Hall of Fame Game, in which a first-half challenge by the Denver Broncos resulted in a 43-yard interference call against them being upheld. Two challenges took place Thursday where coaches argued that pass interference should have been called: one in the Patriots-Lions game, where a challenge by Lions coach Matt Patricia was unsuccessful, and one in the Jets-Giants game, where the Giants received a 33-yard penalty after the Jets’ successful challenge.

Under the new rule, teams can question interference calls and non-calls under the existing coaches’ challenge system in the first 28 minutes of each half. In the final two minutes of each half, an interference-related review would have to be initiated by the replay assistant in the press box.

“I feel like the NFL officiating department and our coaches have spent a lot of time working on this,” said Atlanta Falcons President Rich McKay, chairman of the NFL’s competition committee. “I feel very confident that we’re getting on the same page and we’re going to be able to successfully implement this change.”

The competition committee previously resisted making judgment calls by the officials, such as pass interference, subject to replay review. But the furor over the Rams-Saints fiasco changed everything.

The potential problem with the new system is that while no one would dispute that the Rams’ Nickell Robey-Coleman committed interference when he plowed into the Saints’ Tommylee Lewis before a Drew Brees pass arrived late in regulation, it won’t always be so clear-cut whether a defender’s hand placed on a receiver’s shoulder, or a relatively subtle tug or push, should result in a penalty.

“One thing everyone will agree on is we needed a system to correct that egregious, ‘Oh, boy,’ jump-out-at-you play ... [but] we’ve added a subjective portion of the game to replay,” said Parry, the referee for last season’s Super Bowl, who retired from the NFL in April and is now a rules analyst for ESPN. “I think we fell short a little bit. I’d like to see player safety be part of the discussion. That same play was an illegal hit to the receiver’s head.”

With the league’s officiating department in New York in charge of replay reviews, the success of the new system depends on the judgment of Al Riveron, the NFL’s senior vice president of officiating. Many within the league were displeased with Riveron’s handling of replay reviews on catch-or-no-catch calls a couple of years ago, suggesting Riveron was too focused on re-officiating plays via the minutiae of replay rather than merely correcting blatant mistakes.

“It has to be obvious,” an executive with one NFL team said of replay for interference, speaking anonymously to provide a frank assessment of the new rule. “If you and I are arguing about it, it shouldn’t be overturned. ... I think [Riveron] learned his lesson a couple years ago on catch-no catch. That’s why we had the new catch rule. ... It can’t be possibly wrong. It has to be obviously wrong.”

Some within the sport worry that fans, TV viewers and even broadcasters won’t be ready for the first time a touchdown comes under automatic replay review (as all scoring plays do) and is negated by an illegal pick — constituting offensive pass interference — that sprung open a receiver but went uncalled on the field. And what if replay catches an offensive lineman blocking a few yards downfield on a run-pass option play with the pass in the air? That’s offensive pass interference, too.

“I am disappointed in that because it’s going to take away from the game,” Ty Law, the Hall of Fame cornerback for the New England Patriots, said in a conference call. “You know, referees are out there for a reason. Yes, they don’t make every call right. But something like that, a pass interference, once you start opening that can of worms, it’s going to get ugly, and the game’s going to get a lot longer.”

There is fretting that games will bog down in the final two minutes when the replay assistant calls for a review of, say, an inconsequential two-yard pass. But mostly, the burden of whether to initiate interference-related reviews falls on coaches. They remain limited to two replay challenges per team per game (plus a third if the first two are correct). That should keep the number of interference-related reviews relatively in check, but coaches must deal with an additional layer of in-game strategy and source of sideline angst.

“It’s going to be a very stressful deal for us,” Washington Redskins coach Jay Gruden said last week. “It’s got to be obviously blatant for them to overturn a call or put a flag on a field. But it’s something we’ve got to watch out for. These plays are huge, and then you have to decide what play is big enough to challenge where you don’t want to waste a challenge, maybe, on a 12-yard gain. But if it’s a 12-yard gain on third down and 8, maybe you do if it keeps the drive going.”

This marks the NFL’s first foray into allowing replay to impose a penalty for an infraction that went uncalled. If it goes well, it could be a step toward further expansion of replay, perhaps ultimately toward a system in which all calls or non-calls could be challenged — something that Patriots coach Bill Belichick has proposed in the past. But first, this attempt has to work out.

Parry participated in the replay-for-interference deliberations at the NFL combine before retiring. He said he’s concerned that so many decision-making thresholds are in play under the new system: the standard for the on-field officials to make the initial ruling; the standard for a coach deciding whether to challenge; the standard for the replay assistant to stop a game and initiate a review; and the standard for Riveron and the NFL officiating department to overturn a call.

“With all these different standards,” Parry said, “there’s going to be some growing pains. But hopefully, with time, we get it right.”