Art McNally, the first on-field NFL official to be inducted into the Hall of Fame, passed away Sunday at 97. A cause of death has not been released. 

Credited with the implementation of instant replay, as well as the NFL's formal officials training program, McNally has been celebrated as the 'Father of Modern Officiating.'

'Art McNally was a quiet, honest man of integrity. To see Art's decades of service recognized with his enshrinement as part of the Class of 2022 was a special moment for the Hall,' Hall of Fame president Jim Porter said in a statement Monday. 'His legacy as a strong leader who helped usher in the advanced training of officials and the technology necessary to keep up with a faster and more complicated game will be preserved forever in Canton.'

NFL commissioner Roger Goodell also released a statement: ​'Art McNally was an extraordinary man, the epitome of integrity and class. Throughout his distinguished officiating career, he earned the eternal respect of the entire football community. Fittingly, he was the first game official enshrined in the Pro Football Hall of Fame in Canton, Ohio. But more importantly, he was a Hall of Fame person in absolutely every way. Our thoughts go out to his wife, Sharon, his children Marybeth, Tom, and Michael, and his grandchildren.'

There couldn't have been a more appropriate choice for Canton than McNally, whose fingerprints are all over how games are officiated even today.

After a nine-year career on the field, McNally overhauled the department when he took it over in 1968 and remained involved until retiring in 2015.

'He really pulled it all together. He kind of took it from an avocation to a profession and set the stage for everything that came after that,' former NFL referee Ed Hochuli said.

'It's been obviously a long time that there have been no people from the officiating side who have gotten into the Hall of Fame. There have been some incredible officials along the way who can make a great argument they ought to be in the Hall of Fame. But none of the officials would disagree that if there's only one or if there is a first, Art McNally should be the guy.'

McNally got his start in officiating in an informal way when he called games while serving in the Marines in World War II. He went on to call more than 3,000 games in football, basketball and baseball, chronicling them all in books he kept, according to son-in-law Brian O'Hara.

Before shifting to the NFL league office in 1968, McNally would often officiate high school, college and professional games on the same weekend.

'He was natural at it,' O'Hara told the Associated Press before he was inducted into the Hall of Fame back in August. 'From being a teacher and being kind of like a rule follower his life because he followed the rules. ... The biggest thing was he enjoyed making it fair. That's all he wanted to do was to be fair and to get it right. I guess that's the things he enjoyed about officiating.'

O'Hara said McNally never thought the day would come when he would make it into the Hall of Fame because officials typically are only noticed when they missed calls.

But McNally didn't shy away from the scrutiny; he had a listed phone number and often took complaint calls from aggrieved fans from various teams that he would listen to as long as they remained civil.

O'Hara said McNally even forged a relationship with a disgruntled Bears fan, with McNally once making a surprise visit to his barbershop in Chicago and getting the fan tickets to the Super Bowl.

McNally's biggest impact came in how the NFL evaluated and trained officials in a system that is still mostly in place today.

Under his watch, the NFL standardized how officials worked a game in their positioning and what calls they made to bring more consistency to the sport.

He used all-22 game film to teach the officials and grade their performance, using the film to teach as well as evaluate officials. He utilized weekly training videos and rules quizzes to help improve the officiating across the league.

'That was brand new,' said Dean Blandino, one of McNally's successors as the NFL's head of officiating. 'That was kind of cutting edge. People weren't doing it. Art came in and understood that this was something that was needed and laid that foundation and that foundation is still what we stand on today in the officiating world. Every league in every sport at every level has an evaluation system and that all goes back to Art.'

McNally also helped implement the NFL's first use of instant replay in the 1980s and got his first chance to work a Super Bowl as a replay official following the 1986 season.

That version of replay was abolished in 1991, but McNally provided guidance to his successors when replay returned in 1999, as he was steadfast in his belief that the league should use any tool to help officials make the correct calls.

'You just want to get it right,' Hochuli said. 'Art was the definition of that. If you look up the definition of integrity in the dictionary and there's a picture of Art.'