PHOENIX -- NFL commissioner Roger Goodell, standing with other league executives in front of a backdrop emblazoned with the league's new 100th anniversary logo at the Arizona Biltmore hotel, announced on Tuesday that the league would allow pass interference to be reviewed via instant replay in 2019.

Amid jubilation from coaches and notable relief from owners, the man who must convert this overdue and complicated change into a credible reality stood quietly to the side. Al Riveron, the league's senior vice president of officiating, faces months of difficult work before teams head to training camp in July.

Atop his list: establishing a consistent standard for overturning the judgment of officials on the field.

Replay isn't intended to re-officiate calls on the field, but instead to correct clear and obvious mistakes. It's one thing to decide whether a player clearly fumbled or crossed the goal line, the kind of objective decisions replay has been assisting for years. But it's quite another to judge whether one player materially restricted another from catching the ball. A number of coaches who supported some level of officiating intervention this week appeared fearful that a "clear and obvious" standard would be difficult to find.

"To think that the two of us are ever going to agree on 'Is it or isn't it pass interference,' that will never happen," said Oakland Raiders coach Jon Gruden, a former ESPN analyst. "For us to think that we can look at a replay at super, super super slo-mo of pass interference and determine whether it is or it isn't, I think is unrealistic. I tried to do it in a booth for nine years. Me and Gerry Austin, who [refereed] in three Super Bowls. We couldn't tell if it was or wasn't. We disagreed. And I just think it's very, very difficult for any of us to see if it's that speed.

"Certain guys look at things differently. We're not going to look at this cup of coffee the same way. It's too hot. It's too cold. But we're still going to drink it and we're still going to move on to the next play."

The good news is that there is precedent for such a change. The Canadian Football League has been reviewing pass interference since 2014. After a few adjustments, the league settled into a groove and even saved itself from a tainted outcome in the 2015 Grey Cup.

Riveron's job will be difficult, but far from impossible. The NFL started its replay expansion with pass interference because, as a spot foul, it leads all penalties in impact on the game. But Goodell and others were not shy Tuesday about suggesting this one-year experiment could serve as a gateway for further replay expansion in future seasons.

Here is a look at other notable rule and bylaw changes owners considered in their abbreviated two-and-a-half-day meeting:

Elimination of all blindside blocks

It is now a 15-yard penalty if a player "initiates a block in which he is moving toward or parallel to his own end line and makes forcible contact to his opponent with his helmet, forearm or shoulder." Previously, a blindside block was legal unless the blocker contacted the head or neck area of the opponent.

A leaguewide study of punts, which surpassed kickoffs in 2018 as the play with the single-highest injury rate, led to this rule change. (About 10 percent of all major injuries occur on punts.) But this rule covers all plays, not just punts. The league's internal study revealed 10-12 concussions occur every season on blindside blocks, sometimes on punts but also during "sudden change" plays such as interception or fumble returns.

Kickoff changes made permanent

The original 2018 kickoff changes were made for one season only. But a 38 percent reduction in concussions on kickoffs last season compared to the previous three-year average convinced owners to make the changes permanent. The most significant alterations were the elimination of the two-man wedge and a new prohibition on running starts for the coverage team.

The change coincided with a sharp reduction in recoveries of onside kicks, dropping the recovery rate from 21.1 percent in 2017 to 7.7 percent in 2018. Yet overall, NFL players suffered 25 percent fewer concussions in 2018.

Expansion of league-ordered ejections

Last season, owners approved a plan that allowed Riveron to order the ejection of a player who had committed a flagrant non-football act such as punching or fighting. That happened at least once, to Kansas City Chiefs defensive lineman Chris Jones in Week 5.

Now, Riveron will be able to order the ejection of players for flagrant football acts too, such as a hit to the head or neck of a defenseless player. This adjustment gets the NFL closer to the NCAA's targeting rule, has the potential to impact the outcome of games and could further escalate a trend of increased ejections across NFL games. There have been 38 players ejected in the past two seasons, compared to 17 in the previous two.

Penalty enforcement option after scores

If an opponent commits a personal or an unsportsmanlike conduct foul during a touchdown, the team can now choose whether to enforce it on the extra point/two-point conversion or the ensuing kickoff.

New draft order tiebreakers

The first tiebreaker for determining draft order will remain reverse order of strength of schedule. But when teams finish with the same record and the same strength of schedule, the NFL will no longer turn first to a coin flip. Instead, this rule adds six more traditional tiebreakers, the same that are used to determine playoff spots and seedings. Only if the teams remain tied at that point would a coin toss be used.

Defeated: Onside kick alternative

A proposal from the Denver Broncos would have given teams a one-time opportunity in the fourth quarter to swap a kickoff for a fourth-and-15 play attempt at the 35-yard line. Convert and keep the ball. Don't convert and turn it over. In essence, it would have served as an alternative to the onside kick, an attractive option considering the new difficulty in recovering them. But the proposal was not met with much support. New York Giants co-owner John Mara quipped to reporters, "What are we, the Arena League?"

Tabled: Overtime changes

Owners will spend more time discussing a proposal from the Chiefs to guarantee both teams a possession in overtime. It would eliminate the overtime coin flip, instead allowing the winner of the pregame coin flip to decide whether to kick off or receive to start overtime. It also would eliminate overtime in the preseason. It's possible the proposal could resurface during the league's spring meeting beginning on May 20.