Jason Giambi has a deep, dark secret. Deeper than his compulsion to sleep on the side of the bed nearest the door, and darker than his dream of growing up to be a heavy-metal musician.
    
The deepest, darkest secret harbored by the New York Yankees first baseman is that whenever he is in a prolonged hitting funk, he wears a gold lamé, tiger-stripe thong under his uniform. "I only put it on when I'm desperate to get out of a big slump," he confides.
   
Over Giambi's checkered career in the Bronx, he has left the "golden thong" in the lockers of slumping teammates Derek Jeter, Bernie Williams, Johnny Damon, Robin Ventura, and Robinson Cano. "All of them wore it and got hits," he reports. "The thong works every time."
   
This season, the 37-year-old Giambi could stand a good thonging or two. He is in the final guaranteed season of a seven-year, $120 million contract, and through Wednesday was batting an obscenely low .188 with seven homers and 20 R.B.I.'s in 33 games for the sputtering Yanks.

Though he can still swat long flies and work bases on balls, against power pitchers-those who strike out or walk more than 28 percent of batters faced-he has often looked outmatched.

"I never hear the boos because I'm too busy booing myself," he says. "No critic is worse on me than me: I can beat myself up pretty good."

Off the field, Giambi is a freewheeling character with a smile as wide as the gap in left center at Yankee Stadium. He loves strip joints, cites Letters to Penthouse as his favorite work of literature, and lives by the motto "Party like a rock star, hammer like a porn star, rake like an all-star."
    
"I'm a year older than Mickey Mantle was in his final game," he says. "My teammates used to call me the Modern-day Mick because I could play all day and party all night. Now I'm more of a family guy. I drive an Escalade to the ballpark."
   
Mantle, of course, was a Gold Glove center fielder. Giambi has a cold glove and an icicle of a throwing arm. He would make a splendid designated hitter if not for an inability to focus when coming off the bench. He's a much sharper hitter-his lifetime batting average is about 60 points higher-when he plays the field.
   
"When I D.H., my numbers are terrible," Giambi says. "I don't know what it is. When I play first base, it gives me something to do." Unfortunately, none of his understudies are batting much better this season.
   
Giambi's 2008 salary—$23.4 million—is the second highest in the majors, behind only Alex Rodriguez. "There's no such thing as perfect happiness," Giambi says with a sigh.
   
"I wish there was, but that's not life. Whenever something perfect happens you can always count on something else going wrong. As much fun as I had during my ‘comeback season' in 2006, life was bittersweet. My dog got cancer."
   
Giambi's career numbers as a Bronx Bomber seem to confirm the notion that ballplayers 30 years or older never merit contracts of seven or more years.
   
Only three players have ever justified such long-term, big-money deals: Derek Jeter, who in 2001 signed for 10 years and $189 million; Manny Ramirez, who in 2000 got $160 million over eight years from the Boston Red Sox; and A-Rod, whose 2000 free-agent pact with the Texas Rangers was for $252 million and spanned 10 years. At the time of their signings, all three were 28 or younger.
   
Giambi was 30 when he first donned pinstripes. He had won a Most Valuable Player Award in 2000 and was runner-up in 2001 with Oakland before turning free agent and rejecting the Athletics' offer of six years at $90 million—40 percent of the team payroll. "A coach once told me to play as hard as I could, perform well, and money would be thrown at me," he recalls. "The coach was right."
   
He took the money George Steinbrenner was throwing at him and headed east, where his production all-too-quickly went south, largely because of injuries connected to steroid use. From 2004 to 2007, he averaged 110 games a season, missing a third of the Yankees' games.

When this season ends, the Yanks could pick up Giambi's 2009 option for $22 million. Or they could pay him $5 million to go away. Though Giambi would happily take a pay cut to stay in New York—"Money doesn't drive me," he says—the team will likely give him a buyout and invest in younger, less limited talent. No doubt he'll sign on with another franchise, quite possibly the A's.
   
Giambi doesn't plan to hang up his cleats just yet, but he's not exactly ruing the day he does. "After A-Rod retires, he wants to be a real estate mogul, the next Donald Trump," Giambi says. "I could care less. As long as I can have a fast boat and a margarita machine and can light my hair on fire, I'll be just fine."