But Bowles quelled his frustration and assessed each situation, just as he learned to do by growing up in a housing project rife with crime and drug abuse, or by decoding offensive formations in a nanosecond as an N.F.L. free safety, or by devising such hellacious defensive game plans that mentors wondered how a modest man could unleash such fury on the field.

Billy Nagy, one of Bowles’s former football coaches at Elizabeth High, said that when he watched Bowles’s news conferences, he was reminded of the mature guy who played for him 35 years ago — same confidence, same composure.

Rodney Carter, one of Bowles’s lifelong friends, said: “In all my time knowing him, nothing’s ever really gotten to Todd. He was always in control. You know that commercial, ‘Never let them see you sweat’? That’s him.”

Instead of submitting to the temptations that suffused the Pioneer Homes project, Bowles, 51, inherited his resolve from his mother, who, after divorcing his father, raised four children while juggling jobs as a librarian and pharmaceutical lab assistant. He did not smoke or drink or do drugs. His lone vice, friends say, is Chips Ahoy cookies, which he would take to restaurants and eat, complemented by two glasses of milk.

Bowles abides by the adage “He who hesitates will be left,” spoken by Flip Wilson’s character in the 1974 comedy “Uptown Saturday Night.” The portrait of him that emerges from interviews with nearly 30 people who know him well is of a man who has been preparing most of his life for this moment: his first game as a noninterim N.F.L. head coach, Sunday against the Cleveland Browns.

He has the can’t-surprise-me mettle of someone who not only witnessed a murder outside a pizza parlor but also had to adapt after being elevated twice during seasons to replace fired coaches. He has the humility of an eight-year N.F.L. veteran who arrived at his first training camp scrapping for a roster spot and wound up retiring a Super Bowl champion. He has the credibility to relate to the emotions and insecurities that can undulate through a locker room.