Cheyenne Westphal. Photo by Monika Hoefler.

The contemporary art expert Cheyenne Westphal, who left Sotheby’s in March after 25 years, announced yesterday that she will join the house’s smaller competitor Phillips next spring.

Westphal, whom Harper’s Bazaar called “Sotheby’s secret weapon,” resigned from her post as world-wide head of contemporary art at Sotheby’s amid an unprecedented string of exits by high-profile veterans. At Phillips, she will take the position of chairwoman. According to the Wall Street Journal, which has the story, Ed Dolman, CEO and chairman of Phillips, will cede the latter title when she starts next spring.

Westphal’s departure took the art world by surprise. She joined Sotheby’s in 1990 and oversaw every major contemporary art sale in Europe since 1999. She is credited with getting Sotheby’s some of its most high-profile consignments, including several artworks featured in Wednesday’s contemporary art sale in New York, and its top lot, a Cy Twombly chalkboard painting that changed hands for $36.7 million.

Westphal was also key in organizing the highly unorthodox Damien Hirst two-day auction “Beautiful Inside My Head Forever,” in which the YBA brought his own works directly to the auction house. That 2008 sale in London, which coincided with the collapse of Lehman Brothers, achieved $200 million, signaling a market peak at the time.

“Phillips has a lot of momentum,” Westphal told the WSJ. “It’s growing, and I think I can bring something to the equation.”

Indeed, while the two rival auction houses Christie’s and Sotheby’s are seeing major shifts in staff, Phillips has been taking the opportunity to bulk up its contemporary department, particularly with the help of Dolman, the former CEO of Christie’s, who has been mining his relationships there to bring top talent to Phillips.

Earlier this month, Phillips announced a major expansion of its international team of art specialists with the addition of three seasoned specialists to its 20th-century and contemporary art department, and one new addition to its Latin American art team.

According to the WSJ, auctioneer Simon de Pury, who sold Phillips to Russian retailing giant Mercury Group in 2008, called Westphal’s hire “a coup.” He told the WSJ, “Getting Cheyenne on board is a huge step for Phillips. There are really only a few major players in this industry, and she’s one of them.”

Her exit from Sotheby’s could have been linked to the auction house’s $85 million purchase of Art Agency, Partners in January, a private consulting firm founded by ex-Christie’s contemporary head Amy Cappellazzo and high-powered advisor Allan Schwartzman. The advisors were given mandate by Sotheby’s CEO Tad Smith to boost sales of contemporary art, potentially stepping on Westphal’s toes.

An earning report released earlier this week revealed that Sotheby’s revenue fell by almost a third in the first quarter of 2015.