When a sellout crowd of 48,231 witnessed the first pitch at the $1.5 billion Yankee Stadium on April 16, 2009, the iPhone hadn't even turned 2 yet. Back then, there was no way of knowing that the stadium's stiffest competition for fans' attention would someday come in the form of omnipresent smartphones.

Eight years later, the social media revolution those phones helped spawn has reshaped the ballpark -- literally.

Social media, most notably Snapchat, Twitter, Instagram and Facebook, has transformed the fan experience, pushing teams such as the Indians and Rockies to innovate on the fly as they try to appeal not only to millennials, but to the next age group -- Generation Z, roughly defined as people born in 1995 or later -- whose lives are focused online.

The Yankees are next up. In April, they will join this budding ballpark trend, unveiling what owner Hal Steinbrenner described as more "family friendly" and "socially oriented" spaces at Yankee Stadium.

Those spaces include play areas for young children and different vantage points for ticket holders to mingle and, most important, take pictures, videos and selfies they can share on social media. The Yankees declined to say how much they have spent on the project, but, for other teams, it has ranged between $10 million and $60 million.

"Baseball is generational. We are being proactive." Yankees senior vice president Marty Greenspun

The Yankees' attendance has dropped nearly every year since their new digs opened, falling from an average of 45,918 its first year to 37,820 last season, and the team views the remodeling of the stadium as both a long-term play to hook Generation Z into the pinstriped experience and a way to give millennials and older generations new ways to experience the game.

"If that's true, then it's a really interesting innovation because, in the case of the Yankees, they're trying to do something about an issue that has been present in the conversation of people who own teams now for 20 years," said Roger Noll, a Stanford University professor emeritus who has written extensively on the business of sports stadiums.

While the trend still is burgeoning in the major leagues, it might soon become a necessity. The Rockies jumped in last year with a $10 million renovation of Coors Field to further take advantage of its beautiful mountain views.

"You have to do it because, if you don't, fans are going to go someplace else," Rockies chief operating officer Greg Feasel said. "There's so many choices now for the consumer, for the fan and you've got to give the fans what they want, and if you don't, they're going to go find it someplace else."

That begins with the ubiquitous smartphone, which is incessantly vying for attention. What remodeling baseball executives are attempting to do is turn those devices from potential adversaries to partners.

WAR and BABIP? Try FOMO and FOBO

The current age of baseball has been inundated with new acronyms, from OPS to WAR to BABIP, but when it comes to retooling the stadium experience, there are a couple of vital ones to learn -- FOMO and FOBO.

Fear of missing out (FOMO) is one phenomenon of social media in which people feel left out because of friends' social feeds. When people attend games, they can tell their little social world, "Look at me, I'm here." They can do that now, from their seats, but fans want to let their friends in on the full experience -- and perhaps show off a little.

For any entertainment entity, fear of being offline (FOBO) is a term that also has more and more relevance. It is the need, maybe even obsession, particularly among the ranks of Generation Z, to constantly be connected to the internet.

"You have the next generation of kids that come to games with their parents and really need to be online all the time," Yankees senior vice president Marty Greenspun said.

Now, with a new-look bleacher section, it'll be even easier for Yankees fans to have their beer and take a selfie with it too. New York Yankees

From Hal Steinbrenner on down, the Yankees have been studying this trend and how to adapt their stadium. After realizing that people, young and old, most like to share photos and video on social media, they have tried to create experiences beyond the game where fans can film themselves.

By eliminating about 2,100 seats -- half were obstructed and cheap in the bleachers -- they believe they have created a less stagnant environment. (To make up for the loss of the cheap seats, the Yankees say they have added 200,000 tickets priced at $15 or less, which averages out to nearly 2,500 per game.)

For all the talk of social media, however, criticism of the ballpark's design has dogged it since day one. The new additions are sponsored, which probably means they'll have to be done just right to overcome the stadium's corporate atmosphere. Since it opened in 2009, expensive ticket prices, the cave-like feel to Monument Park, the infamous moat that separates the field-level luxury seats from the rest of the stands and the lack of fans sitting behind home plate in those luxury seats -- an incessant TV eyesore -- have caused many "common fans" to feel left out. During a dispute with StubHub over discount ticket prices, Yankees COO Lonn Trost drew headlines -- and mockery from late-night television -- when he asserted that ticket-holders in luxury areas don't want to sit next to fans who have "never sat in a premium location" before.

The Yankees came up with the renovation plans after commissioning studies and surveys.

There is the nearly 3,000-square foot "SunRun" Kids' Clubhouse on the third level in right field, which will have a six-foot World Series trophy replica and private spaces for nursing mothers. The idea behind it, Steinbrenner said in a press release, is for "our youngest fans to feel as if Yankee Stadium is an extension of their local park or backyard."

For Generation Z, millennials and older fans, there will be a 3,500-square foot space on the second level in center field called the Master Card Batter's Eye Deck. Nearby, there will be the Bullpen Landings, which will feature specialty food and a bar that, as its name denotes, will give fans a chance to peer at relievers in the bullpen. The AT&T Sports Lounge will be on the field level and essentially be a sports bar without much of a view of the field. And the new Budweiser Party Decks in sections 311 and 328 will feature bars -- and a view of the game. They're also installing charging stations in the new locations -- adding more than 125 USB ports, about three times the number that currently exists in the non-suite areas of the stadium (and all of which have been added since August 2015) -- for fans to top up their devices.

"They are trying to respond to how younger people want to experience ballgames," said Andrew Zimbalist, a professor of economics at Smith College.

The Yankees believe what fans want are more social areas that overlook the field, since they watch games differently than they did a decade ago. If all goes according to plan, parents with young children will have more options to occupy their kids' attention, while older kids and adults will have more places to snap photos and videos with their family and friends.

"Baseball is generational," Greenspun said. "We are being proactive."

The new stadium brought over the same look as the old stadium in terms of how the field is configured. The Yankees believe they have maintained it, even with the new areas.

For the traditionalists, they can still watch the game, from their seat, for all nine innings, as they always have.

Progressive Field becomes progressive

The remodeling of the stadium experience will mean something different for individual clubs, if, as anticipated, it becomes the new norm instead of an exception. Progressive Field in Cleveland is more than 20 years old. When it was moving into its teens, then-team president Mark Shapiro and his fellow executives began to think about how they could cater to different segments of the city's population. They wanted to bring inside the ballpark a little of what they believe makes Cleveland special.

"What makes our market in Cleveland great is a lot of the great neighborhoods," said Alex King, the Indians' vice president of brand marketing.

Progressive's new area, the Right Field District, and other updates, cost nearly $60 million, according to King. It brought local restaurant concessions into the stadium, while creating bars and open areas for fans in right field.

"The trend in stadiums for the last 20 years has been exactly what's going on in Yankee Stadium, which is to make them more and more like shopping centers." Roger Noll, a professor emeritus at Stanford University, who has written extensively on the business of sports stadiums

"It was really designed for that millennial young professional group," King said.

However, officials believe these areas appeal to more than just young people.

"I think it's a little bit too early to tell," King said. "I think trying to always be relevant to your fans and listening to them and trying to understand what they are looking for, we're always going to try to do that. Ultimately, is that something we can continue to see accelerate or be something that is in demand? I think it is pretty early for us."

Mile High ideas

From The Rooftop at Coors Field, fans can see spectacular views, some of which also include a clear look at the field. Three years ago, the Rockies took full advantage of the gorgeous mountain vistas. They ripped out some mostly unused seats and put in the rooftop area in right field.

"We've got two cabanas that we put up there and we stole that idea from Vegas or The Broadmoor [a luxury resort in Colorado Springs], and you can't even see the field," Feasel said. "We sell those things out."

"You have to do it because, if you don't, fans are going to go someplace else. There's so many choices now for the consumer, for the fan and you've got to give the fans what they want and if you don't, they're going to go find it someplace else." Rockies COO Greg Feasel

For sports teams, there is a clear business component to the changes. Not only do they want to give fans different views of the games and different experiences, but they want them in the stadium earlier and longer. One way to entice young people is with beer, which the Rockies charge only $3 for before games.

Noll, the Stanford professor, said this is part of a larger trend to take what used to go on outside the stadium and move it inside.

"The trend in stadiums for the last 20 years has been exactly what's going on in Yankee Stadium, which is to make them more and more like shopping centers," Noll said.

The game is still the centerpiece, but there is more and more to complement it. The Rockies' Rooftop sign that reads "5,280" is a prime selfie spot, as people share that they are a mile above sea level.

It is all part of making the experience more than just a game -- designed to use the phone as a tool in the stadium experience instead of a distraction. Yankee Stadium is the latest to have a social media makeover, but it likely won't be the last.