The Brooklyn venue replaced Ticketmaster, the industry leader, in 2021 in favor of SeatGeek, a competitor. It is not clear why it changed direction again.In 2021, Barclays Center in Brooklyn made a surprising announcement about its business: After nearly a decade with Ticketmaster, the industry leader, as its ticketing vendor, the arena was switching to SeatGeek, an aggressive upstart.Now, barely a year into what had been a seven-year contract, BSE Global, the parent company of Barclays — the home of the Brooklyn Nets and New York Liberty basketball teams, and a destination for major concert tours — is canceling its partnership with SeatGeek and returning to Ticketmaster.The change was revealed on Friday when Barclays announced a concert by the singer and producer Jackson Wang on May 11 with a link to Ticketmaster. SeatGeek, which remains the ticketer for many events already on Barclays’s calendar, will gradually be replaced by Ticketmaster in coming months as new concerts and sporting events go on sale.The abrupt switch, at a high-profile venue in one of the biggest markets in the world, is head-spinning news in the lucrative ticketing business, where Ticketmaster’s dominance has long been a matter of debate and scrutiny.“It’s very rare for such a cancellation,” said Larry Miller, the director of the music business program at New York University’s Steinhardt School of Culture, Education and Human Development.“Ticketing platform deals with venue owners are not of short duration,” Mr. Miller added. “I can’t think of a time over the last decade where a major venue has dropped a ticketing platform early on in the deal cycle.”The reasons for the change at Barclays were not immediately clear. Neither BSE Global nor SeatGeek would comment about whether there were any problems with ticketing that may have prompted a switch.In a statement, a spokeswoman for BSE Global said that SeatGeek “provided our fans with a first-class game day ticketing experience, and we’re appreciative of the time and energy they put into our work together.”The president of SeatGeek, Danielle du Toit, expressed no upset at Barclays’ change of direction. “It’s never easy to part ways with a client,” she said in a statement, “but as we look to the future, SeatGeek is grounded in our strategy and road map that are geared towards solving the challenges that plague the live entertainment experience.”Since its founding in 2009, SeatGeek has positioned itself as an industry disrupter. Initially just a resale platform, it has sought to challenge Ticketmaster’s dominance in the so-called primary market — sales directly from a venue’s box office, on behalf of sports teams or performing artists. When BSE Global announced its SeatGeek deal, which took effect in October 2021, the venue company praised its new partner’s “best-in-class mobile platform.”SeatGeek’s clients include major sports franchises like the Dallas Cowboys and the New Orleans Saints, as well as Jujamcyn Theaters, one of Broadway’s major theater owners.But SeatGeek, and other ticketing companies, all still lag far behind Ticketmaster, which sold 485 million tickets in 2019, the last year of business unaffected by the Covid-19 pandemic, an amount that swamps its competitors. Regulators have been monitoring Ticketmaster’s market share since it merged in 2010 with the concert giant Live Nation in a deal that critics suggested would damage competition in the ticketing industry, a consequence that Live Nation has denied.As a condition for its approval of the merger, the Justice Department entered into a regulatory agreement with Live Nation that, among other things, prohibited it from retaliating against venues that do not sign with Ticketmaster by withholding shows it controlled. The agreement, known as a consent decree, was extended by five years in 2020 after federal regulators found that Live Nation had “repeatedly” violated it. At the time, Live Nation did not admit to any wrongdoing, and said that extending the decree was “the best outcome for our business, clients and shareholders.”In an interview, Joe Berchtold, the president of Live Nation, acknowledged that the company is always under scrutiny for its actions in the marketplace. In recent weeks, for example, lawmakers have expressed concern over Ticketmaster’s botched ticket sale for Taylor Swift’s latest tour, and the company was widely condemned for its mishandling of a Bad Bunny concert in Mexico City.But Mr. Berchtold was unequivocal in stating that the company did not break any of its regulatory guidelines with Barclays Center.“I can absolutely confirm,” he said, “that there was no retaliation at Barclays for not using Ticketmaster, in terms of the routing of any concerts.”Tracking the blips and dips in tour dates for concert venues can be an inexact science. But data from Pollstar, a trade publication that covers the live music business, shows that Barclays Center received 13 Live Nation-promoted tours in the year after SeatGeek took over the venue’s ticketing business — a drop for Barclays, which in the years before the pandemic had tended to get about two dozen Live Nation events annually.However during the same period, from 2016 through 2019, the data also indicates the venue hosted fewer shows from independent promoters — those not associated with Live Nation or its major competitor, AEG Presents — from an average of more than 50 a year to less than 20 in the year after SeatGeek took over.SeatGeek and BSE Global declined to comment on the data.Barclays Center competes with Madison Square Garden, as well as the Prudential Center in Newark and the new UBS Arena in Elmont, N.Y., for major concert tours to fill out its schedule. Since 2019, BSE Global has been owned by Joseph Tsai, a Taiwanese-born tech billionaire, who bought out its previous owner, the Russian mogul Mikhail Prokhorov. More