For more than a generation the avuncular John Madden was the principal voice of America's most popular game, professional football.

For more than a generation the avuncular John Madden was the principal voice of America's most popular game, professional football.

In his more than 30 years as a broadcaster, the former coach turned announcer appeared on all four networks and was familiar to those old enough to remember his 1977 Super Bowl victory with the Oakland Raiders as to those young enough to tackle his best-selling video game of all-time.

So when Madden announced Thursday that he was leaving NBC's broadcast booth, it sent ripples of surprise through the sporting and television world.

"This is like Johnny Carson retiring," said Robert Thompson, director of the Bleier Center for Television and Popular Culture at Syracuse University. "Carson was not the best comedian, but people loved him. I would not call John the most articulate or analytical mind, but he brought to a football broadcast knowledge and fun that worked even if you didn't care about the game. He was a vaudevillian in the booth."

The gregarious Hall of Fame coach was known not only for his gridiron insights — spiced with colorful stories, loopy play diagrams and occasional songs — but also for his stamp on pop culture, which included his EA sports video game, and pitches for Outback Steakhouse, Sirius Satellite Radio, Verizon Wireless and Ace Hardware.

To colleagues and sports fans, Madden, the only person to work as a lead analyst at all four networks, was the jolly guy who cruised from game to game in a well-equipped bus he called the "Madden cruiser" because he hated to fly. He was the amateur cook who on Thanksgiving Day games would always make sure to show a mouthwatering version of the terducken — chicken stuffed into a duck stuffed into a turkey.

"He brought such a big as life personality with the combination of insight and fun, of everyman enjoyment," said NBC's Bob Costas, host of the network's "Football Night in America" studio show. "And with the Madden video game, that connected him to the younger generation and players. A lot of players play Madden, he was able to do that into his 70s. He stayed contemporary."

The decision to retire ultimately came down to family, particularly his grandchildren, said Madden Thursday morning on the San Francisco Bay Area's KCBS radio, where he appears in regular segments called "The Daily Madden." In the 12-minute interview, he also lamented missing much of the two sons' childhood because he was on the road.

"My grandkids know when I'm gone and when I'm not," he told the radio audience. "You go away in August and you come back in January. I just got to the point in my life where that's not the deal anymore."

He recognized that his rationale may be treated skeptically, but insisted it be taken at face value. There's no contract dispute or darker, undisclosed motive around his departure.

"There's nothing wrong. Everyone is going to say 'Madden retires, what's wrong.' There is nothing. There is nothing wrong with me," said Madden, who was reportedly making just under $10 million a year at NBC. "At some point you know you have to do this."

When Madden told NBC of his retirement plans, NBC executives flew out to California to talk him out of it. NBC Sports head Dick Ebersol tried during an all-day meeting to convince the announcer to postpone his leaving until next season or to at least take a part-time gig this season.

"I knew right away there was no way of talking him out of it," said Ebersol during a conference call with reporters. "I knew in his voice he really thought about this."

This fall will be the first time since Madden's freshman year of high school in Daly City, California that he won't be involved in football as either a player, coach or analyst.

"John could have stayed there as long as he wanted to," said Al Michaels, Madden's broadcast partner inside the NBC booth. "He's got a very organized mind, he doesn't make rash decisions. It's not going to come September and John will change his mind. This is what he wants."

Later Thursday, NBC announced that former NFL wide receiver Cris Collinsworth, who had been anchoring the network's football show, would replace Madden in the Sunday Night booth.

"John Madden broadcast football with a unique passion and style," said Collinsworth in a statement. "Without question, he is the greatest sports analyst of all time."

Madden's career in television began after he retired as the coach of the Raiders in 1979 and joined CBS where he teamed up with Pat Summerall, the former New York Giants placekicker. In 1994, when CBS lost the rights to the NFL, Madden moved to Fox. Then, in 2002, he left for ABC's "Monday Night Football," before finally moving in 2006 to NBC's "Sunday Night Football."

(Optional add end)

Madden's exit, distressing as it may be to some fans, is likely to have minimal impact on ratings. Analysts have long noted that viewership for football games is heavily dependent on the quality of the match-ups and the closeness of the games, rather than the announcing team.

Though Madden was successful as a coach — he was inducted into the NFL Football Hall of Fame in 2006 — he truly rose to prominence as an announcer.

"He came of age in the era of 24/7 sports," said Michael Oriard, a professor of English at Oregon State University who has written extensively about sports marketing and the NFL. "He really explained football. He was one of the first that enabled passionate fans who didn't know zone defense from a man-to-man to enjoy the game, and he explained it in a way that made experts of everybody. His love of the game was infectious."