LEXINGTON, Ky. — Five years ago, Mike Repole was living the dream. He had already made his share of an estimated $4.1 billion fortune from the sale of the company that produced Vitaminwater, and now he had himself a Kentucky Derby favorite with a horse named Uncle Mo.

Repole would regale any and all about growing up in Queens, New York, near Aqueduct, heading the track after school, making bets and loving horses.

But Uncle Mo never made it to the Derby. A day before, he was withdrawn from the race because of what turned out to be a life-threatening liver ailment. The lightning-fast colt recovered, ran again and won, but was never the same. He was retired later in the year. Repole called Uncle Mo the best horse he’ll ever own.

And he wasn’t even talking about Uncle Mo’s life after racing. As a stallion, at stud in the breeding shed. With just his first crop of 3-year-olds, Uncle Mo already is a leading sire in North America — “red hot,” according to Coolmore Ashford Stud, where Uncle Mo is performing with mind-boggling success.

He’s the proud sire of three of the 20 3-year-olds running in Saturday’s Derby — from morning-line favorite Nyquist to long shot Mo Tom to a horse Repole owns, Wood Memorial winner Outwork. Tapit, a leading sire the past several years, also has three offspring in the Derby, but for a young sire like Uncle Mo to be so productive so early is rare.

“I always knew Mo was a once-in-a-lifetime horse,” said Repole, who has made several visits to Ashford Stud, including Wednesday before the Derby draw in Louisville. “What I didn’t expect five years ago was he would give me offspring that were brilliant also. I never thought Uncle Mo would be a better sire than he was a racehorse, but he’s going to be.”

While Outwork already has accomplished something Uncle Mo didn’t — winning the Wood — it’s Nyquist who’s been this year’s sensation for owner J. Paul Reddam. Like Uncle Mo, Nyquist won the Breeders’ Cup Juvenile and was voted 2-year-old champion. Entering the Derby he’s 7-for-7; Outwork is 3-for-4 and Mo Tom won the Lecomte and ran second in the Louisiana Derby.

“Uncle Mo’s oldest crop are only 3-year-olds, but his success so far is unlike anything we have seen for a long time,” Ashford’s manager Dermot Ryan said. “It’s fair to say that Uncle Mo is the hottest young sire in the country and as such he is extremely popular.”

And valuable. His stud fee is up to $75,000, he’s booked for the rest of the season and “the way he’s going that will likely have a big increase next season,” Ryan said.

Some of Uncle Mo’s success: 20 of his 3-year-olds were nominated to the Triple Crown races (the most by any sire) and sales of Uncle Mo’s are soaring — a pair of 2-year-olds recently went for more than $1 million each, and Triple Crown winning trainer Bob Baffert picked out a yearling for $700,000. Repole is buying them up, too. He owns more than a dozen.

Through April 26, Uncle Mo’s progeny totals 585 foals, including 323 of racing age with earnings of more than $8.5 million, according to Equineline.com. Already, he’s having a huge influence on his offspring as a big bay, durable, fast and smart.

“They have size and scope, and they look like him, too. His dominant genes are coming through,” said Todd Pletcher, who trains Outwork and trained Uncle Mo. “What’s great about him is he can put speed into a big horse. They old-timers will tell you that a really good sire will stamp his offspring. He is doing that.”

Doug O’Neill sure is a believer. He trains Nyquist, who has won all seven of his races, including the Breeders’ Cup Juvenile — like Uncle Mo did — and the Florida Derby. His brother, Dennis, picked out Nyquist at a price of $400,000.

“He just really loved the way he moved,” O’Neill said. “And he picks out athletes first, the pedigree is secondary. But once he fell in love with him as an individual, the Uncle Mo was just a huge added bonus because of how good he was.”

Now, O’Neill feels fortunate his brother was at the right place at the right time.

“The other Uncle Mo’s were really looking good in the sales, too, even though none of them had run yet, but there was definitely a buzz about Uncle Mo. Fortunately, we jumped ahead of the hot Uncle Mo train.”

Today, Uncle Mo hangs out with former stablemate Stay Thirsty at Ashford, and heads to the breeding shed in the early afternoons.

“He’s a big, strong horse and is all stallion,” Ashford stallion manager Richard Barry said. “He’s a pleasure to be around and seems to excel at everything he does.”

Repole’s visit on Wednesday went well.

“Spending time with him brings back so many amazing memories,” he said. “You’re supposed to love your children the same, but Mo will always be my favorite.”

For Repole, winning the Wood with Outwork was a great moment he shared with family and friends: “To come back five years later, a New York guy, and winning it? Probably the most special moment I’ve had in my racing career,” he said.

Outwork will be Repole’s third Derby horse. Stay Thirsty ran the year Uncle Mo was scratched and finished 12th. Overanalyze ran 11th in the 2013 Derby.

Just days away from the race, Repole will be one nervous owner.

“The anxiety before the race is not fun,” he said. “The exhilaration after (winning) the race is fun. And to have a horse that’s a son of Uncle Mo in it … You can’t ask for more.”

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