OMAHA, Neb. — Sandlot baseball, a slice of American life enjoyed for decades by boys from coast to coast, appears on the verge of extinction.

Many men over 40 remember those summer days when they headed to the park or vacant lot and played ball all day — or until Mom sent word that it was time for dinner.

Nowadays, most neighborhood ball fields sit empty on summer afternoons, the idea of unsupervised play having gone the way of the rotary-dial phones kids once used to round up the fellas for a game.

The reasons for the sandlot's demise, baseball coaches and sociologists say, go back to the changing family structure, video games, parents' fear of crime, and the proliferation of organized and so-called "select" teams for more talented kids.

Johnny Damon of the New York Yankees says the structured environment of select ball sacrifices the fun kids get from playing on their own.

"I think nowadays kids are getting so worn out playing baseball year-round that by the time they get to the high school level they're kind of tired of it, and tired of the politics of it, instead of just going out there and playing baseball," Damon said.

Dan Gould, director of Michigan State's Institute for the Study of Youth Sport, put it bluntly: "The end of the story is, the sandlots ain't coming back, as much as we would like them to."

The number of ballplayers in the United States has remained fairly constant throughout the years, though studies have shown fewer youngsters from the inner city are picking up the game.

There were 16.1 million participants in 2006, according to the most recent Sporting Goods Manufacturers Association International survey. But almost 12 million of those play in organized leagues, while the remaining 4 million said their most common form of play was "casual."

"That number should be higher," association spokesman Mike May said of the sandlot players.

Don Weiskopf, a 79-year-old retired college professor from Eugene, Ore., advocates a revival of sandlot ball on his Web site, Baseball Play America.

A former player in the Cleveland Indians organization, Weiskopf said youngsters learn the game best in an unstructured setting.

"The fundamentals of baseball must be practiced continually, even at the big league level," Weiskopf said in an e-mail. "The lack of pickup games and sandlot ball today has hurt the development of young players."

Michigan State's Gould laments the demise of pickup baseball games. The 56-year-old spent much of his youth on the sandlots of upstate New York, and he said kids learned more than baseball when they played among themselves.

They could make their own rules, like closing right field when there weren't enough players. Anyone who hit to right would be out.

They could learn negotiation skills. Was it a ball or strike? Was he safe or out? Was it fair or foul?

They learned organization skills, such as how to pick teams equitably or how to reconfigure the teams if one side was beating the other by a wide margin.

They learned how to get along — up to a point.

"What people forget is that, sometimes, the bigger kid ruled the sandlot," Gould said.

Bill Olson, father of former major league relief pitcher Gregg Olson, believes the game has adjusted to a changing society.

Olson, a former high school and college coach, gives more than 200 private lessons a month to players ages 12 to 18 at Ultimate Baseball Academy in Omaha. He said parents are willing to pay for baseball instruction the way they do for piano and dance lessons.

"Just going to enjoy the game on the sandlot, that was fine," Olson said. "But there is a lot of great coaching going on now, more than 15 or 20 years ago."

Weiskopf said playing in an unstructured environment allows youngsters to experiment with different skill sets and get more repetitions.

But Gould said parents are hesitant to let their kids out of sight for fear they will become crime victims.

"Forty or 50 years ago, people didn't worry about their kids going down to the sandlot by themselves and playing all day," Gould said. "Now you're afraid your kid is going to end up on the milk carton. So there are legitimate fears, whether perceived or actual."

Weiskopf said most kids do not play baseball unless registered by a parent for an organized team. Many of the youngsters show up at their first practice having never had contact with the game, as opposed to the kids of yesteryear who learned from siblings and older friends.

"Even the worst players (of my day) had a good idea about the game and its rules because we played it often and learned from each other," Weiskopf said. "Young children are not playing and practicing the game enough today. They are not getting in enough reps, throwing and catching the ball, batting, etc."