On a coaching staff led by great football minds and famously loud screamers, Romeo Crennel stood out by being only the first of the two.

Crennel retired Monday after 50 years in coaching and 39 in the NFL, including working under Bill Parcells and alongside Bill Belichick with both the Giants and Jets. Crennel was affectionately known by his initials during a 12-season stay with the Giants as a special teams coach (1981-89) and defensive line coach (1990-92) that was the longest of his career.

“Parcells had a hammer, Belichick has a hammer, R.A.C. had a soft hammer,” former Giants punt returner Phil McConkey told The Post. “It was just as effective, but it was his own way. That juxtaposition was really good for us as special teamers and for me in particular.”

Crennel, 74, won five Super Bowl rings — two with the Giants and three as defensive coordinator of the Belichick-led Patriots (2001-04) — and twice came close to a sixth. He spent three years as defensive line coach for the Jets, highlighted by a trip to the 1998 AFC Championship game.

Crennel later went 32-63 as head coach of the Browns, Chiefs and Texans. He finished out the 2020 season as interim head coach of the Texans, surpassed George Halas as the oldest person (73) ever to be head coach in an NFL game and earned the respect of an entirely different generation of players such as J.J. Watt, who described Crennel as an “absolute legend of the game and an even better man” on Twitter.

“He believed in me when probably not a lot of other people did,” McConkey said. “There are different ways to be a leader, but you have to be yourself or it comes off as inauthentic and you can’t achieve your goals. He always had incredible words of encouragement.”

Giants head coach Brian Daboll broke into the NFL as a defensive assistant under Crennel with the Patriots and served as his offensive coordinator with the 2012 Chiefs. Crennel’s final job was Texans senior adviser for football performance in 2021 but he still considered the Giants to be a “special place.”

“Football has been my entire life and it’s been a dream come true to coach for 50 years,” Crennel said in his announcement. The statement continued, “I’ll miss everything about coaching and teaching, but the thing I’ll miss the most is being around the guys every day. My goal was to put every player and coach in the best position to succeed, and I consider every guy I coached or worked with a part of my family.”

It was a normal sight in the mid-1980s to see Crennel and McConkey as the last two on the practice field. McConkey, who played at Navy and remains close to the Academy, was choked up Monday as he tied together the memory of those days and the words of late Sen. John McCain.

“The greatest definition of leadership I ever heard is the ability to convince others that they can do more than they think they can do,” McConkey said. “That leadership applies to me, all the guys I played with and thousands of others for 50 years under R.A.C.: The ability to convince us we had more to give than we thought we had to give.”