Come sunset Saturday, Nationals Park will be full not with baseball fans but with 41,000 devotees of another American phenomenon: Joel Osteen.

Second base will become the main stage for the wavy-haired, ever-smiling Texan, whose cast for the 21 / 2-hour “America’s Night of Hope” includes 100 singers and musicians, 1,000 ticket-ripping volunteers, and a six-person social media team to keep Twitter and Facebook buzzing.

Yet, one of the largest religious events in the region since Pope Benedict XVI’s 2008 visit is coming together pretty much outside of the organized church world.

With a few exceptions, there will be no church bus groups or pastor promotions, and many — if not most — of the people who paid $15 for a ticket didn’t hear about the event through their church, because they don’t go to one.

They are probably among the 10 million people who Osteen’s group says watch his weekly TV broadcast, the crown jewel of a mega­ministry built on the concept of a totally positive, in-your-corner God whose list of “don’ts” is pretty short: Don’t lose hope!

Joel Osteen throws out the first pitch April 16 before a game between the Washington Nationals and the Houston Astros at Nationals Park. (Greg Fiume/GETTY IMAGES)

The show flashes ads for the monthly “inspirational” events more frequently than it flashes verses from the Bible. And for people who live within 200 miles of the ballpark, they started getting e-mails 90 days ago, part of the regular communications for the 1 million people who his group says have asked to be zapped inspirational messages from the Osteens. Or maybe they bought one of his best-selling books or downloaded his podcast — one of the most-downloaded in the world — or follow him on Twitter, where he is considered one of the most-followed religious figures.

People love him for the same reason that many others, pastors in particular, shun him: his near-total silence on the subjects of sin, suffering and detailed doctrine.

“My message isn’t real religious,” Osteen said in an interview. “I’ve stayed good in my sweet spot, which is encouraging people, and hope.”

Even local pastors who sometimes collaborate with Osteen’s ministry were cautious about characterizing it. One declined to comment beyond saying that Osteen’s focus on stories of financial prosperity and his lack of emphasis on sin made him too controversial.

But Michael Collins, pastor of the Extraordinary Life Church in Glen Burnie, who has a video of himself with Osteen on his church’s Web site, said: “There are very few pastors who say ‘Let’s go to this as a church.’ People want him to preach all this deep doctrine, and that’s like trying to get a 5-year-old to play” pro sports. “Most people don’t have the basic aspects of faith, and Joel meets them right where they’re at.”

Others were withering about the thinking behind super-popular Osteenisms such as this one: “No matter what may be happening today, God has good things in store for your future!”

“Why do con artists work? Why do multilevel marketing schemes work?” said Kevin Lewis, a theologian at the evangelical Biola University. “The Bible says, if you want to be prosperous, work hard and gain wisdom. Not, ‘Say the right words, and spiritual forces will make you healthy and wealthy.’ ”

James Bailey, a leadership professor at George Washington University’s business school who will be at the ballpark Saturday, found himself drawn into the Osteen vortex about a year ago while flipping through TV channels one Sunday morning.

“He isn’t heavy-handed with the practical elements: Do this or that, or you’re going to hell,” said Bailey, a non-churchgoing Catholic. “There was a light touch. It’s like, ‘This is about your relationship with God. All I’m doing here is helping you find that relationship.’ ”

Experts have been analyzing Osteen’s ministry since it exploded in 1999, the year it began. His pastor-father, John Osteen, died and was replaced at the pulpit by his cameraman son, who had no theology training, no college degree and not a day of pastoring experience. But his appeal was undeniable.

Lakewood Church in Houston grew from 16,000 to 38,000 worshippers in five years under Joel Osteen and to 43,000 today. It is America’s largest church. Its budget last year was $70 million, including $20 million for the television ministry and $5 million for events such as the “Night of Hope.” He’s sold a million books in Muslim Indonesia. Regular Sunday viewers and attendees at the ballpark will be Jewish, Hindu or the kind of people who check “none” when asked to identify their religion.

Osteen’s success says much about American religion in 2012, when “church” can be a bunch of strangers online who may not even be Christian and when one of the few pastors who can fill a baseball stadium preaches about love, not doctrine.

Although Osteen’s staff seems slightly smug about his ability to rise to the top of American spirituality outside of officialdom, the son of a charismatic preacher doesn’t ignore the subject completely. A few years ago, concerned by the number of people he would meet in other cities who considered him “their pastor” even though they had seen him only on television, he launched a network to connect viewers with pastors and congregations in their home towns. About 300 pastors in the United States are in the network, including 11 in the Washington region.

But the requirements to join are minimal. “They don’t have to adhere to a theological standard,” said Osteen spokesman — and brother-in-law — Don Iloff, “except they must teach the goodness of God. That means, you’re not there to beat these people up. God loves them.”