SCOTTSDALE, Ariz. — The East Coast as the center of the American sports universe? Not so much in baseball anymore.

On Thursday, Buster Posey won the MLB Network’s “Face of MLB” vote, defeating Mets third baseman David Wright in the finals of the bracket-style competition, 52 percent to 48 percent.

That had more to do with the Giants’ social-media machine. Once that locomotive heads down the tracks, folks best hop on board or clear out of the way.

However, Posey’s win in the Twitter- and Facebook-fueled contest symbolizes a larger trend. While most of the big sports media conglomerates remain on the East Coast, highlighting the Yankees and Red Sox at all costs, many of the more popular players work on the left coast.

Fanatics.com, the largest online retailer of licensed sports merchandise, reports that since Jan. 1 the top five major-league sellers of shirts, signed memorabilia and other gear all ply their craft in California.

They are, in order, Madison Bumgarner, Mike Trout, Posey, Clayton Kershaw and Yasiel Puig. The Giants are the top-selling team.

“We haven’t seen this before,” said Jack Boyle, president of merchandising for the Florida-based retailer. “There’s always been greater balance out there — East Coast, Midwest, West Coast.”

Some of this is cyclical. Derek Jeter and Mariano Rivera gear moved well as they embarked on their retirement tours. Bumgarner shot to the top of the rankings off his October performance.

But Posey has been a top-seller on Fanatics.com and its related sites for the past five years. Now that Jeter is retired, Boyle said, “I think baseball is looking for the next face of baseball. Buster could be the next big guy out there.”

Wright won Face of MLB last year. This time, Posey beat A’s pitcher Sean Doolittle and Trout in earlier rounds.

“Any time you’re voted on anything by the fans it’s special,” Posey said. “Being here for a while, now I understand how passionate Giants fans are.”

Giants fans are not just passionate, but very tech-savvy. Posey got a boost from the club, which has used social media to goose vote totals for Giants players in the All-Star Game.

Bryan Srabian’s social-media team even changed the name of the Giants’ official Twitter handle to #BusterPosey during the competition.

Posey might be the Face of MLB, but at least since Jan. 1, Bumgarner has been the biggest jersey-seller.

“He deserves any acknowledgment he gets from what he accomplished last year,” Posey said. “I have no problem being passed by the big fella.”

Henry Schulman is a San Francisco Chronicle staff writer. E-mail: hschulman@sfchronicle.com Twitter: @HankSchulman