A decade ago, when the golf course was a de facto playground for the professional set and a young Californian named Tiger Woods was the world's best player, golf looked like an unassailable national undertaking, and corporate players were champing at the bit to get in.

But the business behind one of America's most slow-going, expensive and old-fashioned pastimes has rapidly begun to fall apart. TaylorMade-Adidas Golf, the world's biggest maker of golf clubs and clothes, saw sales nosedive 28 percent last year, its parent company Adidas said Thursday.

"A decline in the number of active players ... caused immense problems in the entire industry, and as a market leader, this hit us particularly hard," Adidas chief executive Herbert Hainer said on a call with analysts.

The sporting-goods giant has taken "some painful measures to restructure and stabilize" its golf division, Hainer said, including listing its slow-selling golf gear at deep discounts and postponing new launches. The coming years, Hainer had previously warned, present even more "significant negative headwinds" for the game.

It's been years since the increasingly unpopular sport of golf plunked into the rough, and the industry now is realizing that it may not be able to ever get out. All the qualities that once made it so elite and exclusive are, analysts say, now playing against it.

The game -- with its drivers, clubs, shoes and tee times -- is expensive both to prepare for and to play. It's difficult, dissuading amateurs from giving it a swing, and time-consuming, limiting how much fans can play. Even what loyalists would say are strengths -- its simplicity, its traditionalism -- can seem overly austere in an age of fitness classes, extreme races and iPhone games.

Even Jack Nicklaus, perhaps the greatest golfer in history, makes a strong argument for why new players aren't flocking to golf.

"I'd like to play a game that can take place in three hours," Nicklaus told CNN in January. "I'd quite like to play a game that I can get some reasonable gratification out of very quickly -- and something that is not going to cost me an arm and a leg."

The number of Americans who said they played golf at least once last year has fallen to one of its lowest point in years, Sports & Fitness Industry Association data show. Even worse for the sport's future: The number of young people, aged 18 to 30, playing the game has sagged nearly 35 percent over the last decade.

"Every macro-indicator that we've been looking at for the past 20 years -- rounds played, number of minorities playing, women coming into the game -- all of these things that we tracked says that there's less people playing," Mark King, a former TaylorMade president and current president of Adidas North America, told HBO's "Real Sports" last year. "I don't like where the game looks like it's going."

Even the golf business' biggest heroes have fallen out of grace. Tiger Woods sliced through a set of disappointing  tournaments, including the worst round of his career, before declaring last month he would take a much-needed break.

That drop-off has hit America's greens and links hard. More golf courses closed than opened in 2013 for the eighth straight year, according to the National Golf Foundation. And the number of course closures has sped up, averaging 137 closings every year since 2011, data from golf-industry researcher Pellucid show.

But it's not just TaylorMade or the courses that are struggling. Dick's Sporting Goods, which bet big on golf in 2006 by buying specialty retailer Golf Galaxy for more than $200 million, has repeatedly acknowledged their bogey, shuttering stores and ending one experiment -- staffing a PGA professional in the golf sections of more than 500 stores -- by firing all of them.

“Golf from a participation standpoint, and how it translates to retail, is in a structural decline," Dick's chief executive Edward W. Stack said in August. "And we don’t see that changing."

The golf industry has made overtures at "growing the game," some of which have pinned hopes on another superstar like Tiger re-invigorating the game. But some are calling for the great game to prepare for even tougher times ahead.

“There’s nobody out there who’s going to save us,” said Pellucid's president Jim Koppenhaver at a Professional Golfers Association of America gathering in January. “We have to save ourselves.”