• by Mark Walsh  @markfwal, May 9, 2013

Major League Baseball is closing the virtual ballpark gates for a new Twitter promotion. From 12 p.m. to 4 p.m. on Friday, @MLB -- the league’s official Twitter account -- will be closed to new followers so that its existing 2.8 million followers can take part in a BlackBerry-sponsored trivia contest.

Participants have the chance to win a range of prizes, including 2013 World Series tickets, BlackBerry Z10 phones, tickets to the game of the winner's choice, MLB.TV Premium annual subscriptions, and $100 MLB.com shop gift cards.

It’s not the first time that @MLB has gone private for a brief period as a promotional stunt. It ran a closed event from noon to 6 p.m. on Sept. 21 in which MLB’s tweets were visible only to its then 2.4 million followers. That campaign, promoted via the hashtag #MLBMembersOnly, ended up drawing 10,000 new followers -- and each of them had to be approved manually while the account was private.

Beyond attracting new Twitter fans, “it’s about rewarding our followers with unique opportunities to engage with our brand, our partner and win great prizes,” said MLB spokesman Matthew Gould. MLB has already begun teasing the event on Friday on its Twitter feed with a tweet reading: “Tell your friends. Tell your enemies. You’ll want to be following us tomorrow from 12-4 PM ET. We’ll make it worth your while.”

The tweet also includes the #mlBBtkakeover hashtag being used to publicize the event, which MLB plans to formally announce Friday morning. While this is the second Twitter contest of its kind that the league has run, it's the first with a sponsor on board. In addition to the Z10 giveaways and the BlackBerry-themed hashtag, @MLB will feature a branded BlackBerry background when the account goes temporarily private.

MLB has been a strong supporter of BlackBerry in the past through its At Bat app, and late last year e-mailed MLB.com users messages teasing BlackBerry 10 devices.

Baseball trivia can be rather arcane, so will the contest questions be along the lines of “How many total bases did Honus Wagner have in 1907?” Gould assures that MLB will be pitching relative softballs, with most questions probably involving finishing famous baseball-themed quotes.