For all his celebrity, Hirst’s stock in the art market has experienced a stunning deflation. According to data compiled by the firm Artnet, Hirst works acquired during his commercial peak, between 2005 and 2008, have since resold at an average loss of 30 percent. And that probably understates the decline—judging from the dropoff in sales volume, collectors aren’t bringing their big-ticket Hirsts to market. A third of the more than 1,700 Hirst pieces offered at auctions since 2009 have failed to sell at all—they’ve been “burned,” in the terminology of the art world. “He has way underperformed,” says Michael Moses, a retired New York University business professor who maintains a financial index for art. “He has lots and lots of negative returns.”

“Great artists, they always go up to a peak, and then they go down to a very low low,” says collector Alberto Mugrabi. “I feel that Damien is one of the most influential artists of our time.” Hirst may care little about critics, but he knows collectors have great power. Advertising executive Charles Saatchi was an early patron, and in recent years, Mugrabi and his family have played a crucial supporting role. Mugrabi isn’t merely an art lover; he’s called his family “market makers.” His father, Jose, who made a fortune in the Colombian garment business, started collecting Warhols soon after the artist’s death, when his most expensive work commanded six figures. He continued buying them on the cheap through the downturn of the 1990s, and the Mugrabis now own the largest Warhol trove in private hands. They’ve followed a similar strategy with Hirst, amassing more than 100 pieces.

“Collectors have to learn to buy art with their eyes,” Mugrabi says, “not their ears.” An olive-skinned international bon vivant, he’s sitting in his Park Avenue office—a Warhol Blue Jackie sits propped against the wall behind his desk—and showing off a desktop picture on his computer screen: four Hirst sharks, suspended in adjoining tanks. “What’s more amazing than that?” he asks.

When asked what the piece is called, Mugrabi shuffles some papers, racks his brain, but the name won’t come to him. Finally, he yells to his secretary in an adjoining room: “Liz, what’s the name of the shark?” “Theology, Philosophy, Medicine, Justice,” she shouts back.

You can hardly blame Mugrabi for letting it slip his mind. Since he acquired the piece in 2008, he’s rarely seen it. While his family keeps a few pieces around the office—one of the artist’s glass medicine cabinets, a bull’s heart impaled on a knife and encased in a transparent box—most of their Hirsts are stored in warehouses in Newark, N.J., and Switzerland, where the animals are removed from their tanks and refrigerated. Another installation includes 30 sheep, two sides of beef, a string of sausages, an umbrella, and a dead white dove. “Just to install a piece is a lot of money,” Mugrabi says.

Ultimately, Mugrabi is investing to make a profit. He’s trying to sell the shark, for instance, and says he has a good offer. But he’s in a tough spot: Like any major art collector, he has to protect the value of his holdings. That means he must prop up Hirst by paying—perhaps overpaying—at auction. Mugrabi says he thinks the acquisition strategy will pay off, as his father’s Warhol investment did. He brings up recently deceased art critic Robert Hughes, who once interviewed him and called Hirst’s art “a cruddy game for the self-aggrandizement of the rich and the ignorant.”

“In another year, nobody will talk about this man anymore,” Mugrabi says of Hughes. “In 2,000 years, Hirst will still be in people’s vocabulary.”