Hank Steinbrenner was driving like he owned the place. “This thing’s got no pickup,” he said, gunning my midsize Hyundai down Steinbrenner Drive in Tampa, Fla. We had just finished lunch on a January afternoon at a Steinbrenner family favorite, an Italian restaurant called Iavarone’s, and were on our way back to his new office at Legends Field in my rental car, which Hank had insisted on driving. As we approached the ballpark, he steered the car up onto the curb, drove it on the main walkway, between the Yankees merchandise store and a small memorial park devoted to Yankee immortals, and came to a stop just a few feet from the tinted-glass door marked “Executive Offices.” “This is where I usually park,” Hank said, stepping out of the Hyundai and tossing me the keys.

Hank Steinbrenner, who will turn 51 next month, bears a disconcerting resemblance to his father, George M. Steinbrenner III. The square, pinched face, the broad shoulders, the barrel chest, even the tiny feet, are all unmistakably Steinbrenner. The outsize ring on one of his nicotine-stained fingers, however, was not a keepsake from one of the six World Series that the Yankees have won during the 35 years his father has owned the team. It was a miniature horse’s head embedded in a diamond-encrusted horseshoe.

Until recently, Hank worked in a kind of self-imposed exile on his family’s 730-acre horse farm in Ocala, Fla., the Kinsman Farm. It was a relatively stress-free, anonymous life that principally entailed attending races, spending his father’s millions at horse auctions and studying bloodlines to find suitable stallions to mate with the Steinbrenner mares. But last year, when his father’s heir apparent, Steve Swindal, was divorced from Hank’s sister Jennifer and forced out of his job as the chairman of Yankee Global Enterprises, things took a remarkable and unexpected turn for both the Steinbrenner children and professional baseball. Hank and his little brother, Hal, f...