Nitrogen, the champion filly defying all limits as she dreams of making history at Keeneland
A winner of nine stakes races, boasting over $3 million in career earnings and never finishing off the board in 18 starts,the daughter of Medaglia d'Oro will chase her maiden Breeders' Cup Distaff (G1) triumph. For the Green family, her story carries a deeply emotional significance
LEXINGTON, Kentucky (Special for Turf Diario).— Nitrogen does not need to win the Breeders' Cup Distaff (G1)to prove she is an extraordinary mare. But a victory this Saturday at Keeneland could elevate her to an even higher plane, reserved exclusively for those horses capable of sustaining top-level excellence over multiple seasons.
The daughter of Medaglia d'Oro, homebred and campaigned by D. J. Stable, will enter her third consecutive Breeders' Cup engagement as one of the leading contenders for the 1,800-meter distaff showpiece, which offers a $2 million purse.
Trained by Mark Casse and regularly ridden by José Ortiz, Nitrogen was already crowned champion at ages 2 and 3.Now, as a 4-year-old, she will aim to add another top-flight success and take a major step toward a third Eclipse Award.
Her racing record features a remarkable statistic: in 18 career starts, she has never finished worse than third, despite competing across both turf and dirt, facing top fillies of her generation, older mares, and even some of North America's premier colts.
“The most remarkable thing about her is her consistency. She has never finished off the board, and we have campaigned her very aggressively across different surfaces and all over North America,” explained Jon Green, who manages D. J. Stable, the outfit established by his parents, Len Green and Lois Green.
Nitrogen's story began on the grass. In 2024, while still a maiden, she finished third in the Natalma Stakes (G1) at Woodbine, beaten less than a length. She backed up that performance with another third-place effort in the Breeders' Cup Juvenile Fillies Turf (G1) at Del Mar.
Those runs earned her the Sovereign Award as Canada's Champion 2-Year-Old Filly.
In 2025, she strung together five stakes wins, the first four coming on turf, until an unforeseen circumstance reshaped her destiny.
When rain forced the Wonder Again Stakes (G2) off the Saratoga turf and onto the main track, the surface switch unveiled an elite new dimension: Nitrogen splashed home to win by 17 lengths over a muddy track.
“If that race hadn't come off the turf, we probably would have kept running her on grass. Very few horses can perform at such a high level on both surfaces,” Casse recalled.
She subsequently lost the Belmont Oaks (G1) by a nose back on turf before returning to the dirt to capture the Alabama Stakes (G1) by a length and a half over Kentucky Oaks (G1) heroine Good Cheer (Medaglia d'Oro).
Her next assignment brought her to Keeneland for the Spinster Stakes (G1), where she finished second by a head to Gin Gin (Hightail), finishing ahead of Scylla (Tapit) and Thorpedo Anna (Fast Anna).
Finally, in the 2025 Breeders' Cup Distaff (G1), she finished runner-up to Scylla, securing her crowning achievement as Champion 3-Year-Old Filly in the United States.
In 2026, Nitrogen reached even greater heights. Her most dominant performance came on June 5 in the Ogden Phipps Stakes (G1) at Saratoga, where she blew away multiple G1 winner Fully Subscribed (Tiz the Law) by 12341243lengths.
With José Ortiz virtually motionless over the final furlong, Nitrogen covered the 1,800 meters in 1:46.93, flirting with the track record of 1:46.64 set by Lawyer Ron (Langfuhr) in 2007.
“I looked back, saw no one was coming, and stopped riding her. Later I found out just how close we were to the track record,” Ortiz reflected.
Yet her most defining performance came in her next start, when Casse boldly stepped her up against male rivals in the Whitney Stakes (G1).
Stumbling at the start, Nitrogen had to press Dubai World Cup (G1) winner Magnitude (Not This Time) through blistering fractions of :23.43, :46.27, and 1:09.65.
Despite the grueling early exertion, she refused to back down. She finished second to current Horse of the Year candidate Sovereignty (Into Mischief), while finishing ahead of G1 winners Antiquarian (Preservationist), Baeza(McKinzie), Magnitude, and White Abarrio (Race Day).
“That sums up what Nitrogen is all about. When it’s time to race, she digs in and gives you every single thing she has,” Jon Green said.
Her most recent start came in the Beldame Stakes (G2), which she won by 234243 lengths following a seven-week layoff.
Casse deliberately targeted that spot to avoid bottoming her out prior to championship weekend: “We knew she wouldn't be at peak fitness, but she didn't need to be. It's like a game of chess: every move has a purpose. I couldn't be happier with how she's doing right now,” he explained.
For D. J. Stable, Nitrogen holds significance far beyond her race record. The operation had previously tasted Breeders' Cup glory with Jaywalk (Cross Traffic) in 2018 and Wonder Wheel (Into Mischief) in 2022, both in the Breeders' Cup Juvenile Fillies (G1).
However, neither of those champion fillies managed to maintain their top form into their subsequent campaigns.
Nitrogen, by contrast, has never stopped moving forward: “Very few horses continue to improve as they get older.That’s what separates the good ones from the truly special ones,” Green noted.
There is also a deeply personal family connection behind her success. Lois Green, who passed away in 2023, helped plan the mating between Medaglia d'Oro and Tiffany Case that produced Nitrogen.
“She was in one of the last groups of horses my mother worked on with me to decide matings. Every time Nitrogenruns, I know she is looking down on us and smiling,” Jon shared.
Furthermore, the family does not view this Breeders' Cup as an automatic farewell to her racing career.
If she remains healthy and enthusiastic, plans call for her to race on in 2027.
A third consecutive championship campaign would place Nitrogen in elite company alongside Hall of Famers Susan's Girl, Forego, Seattle Slew, Affirmed, Spectacular Bid, John Henry, Skip Away, Azeri, Zenyatta, Royal Delta, and Beholder.
For now, the immediate challenge remains Saturday's Distaff. Boasting nine stakes victories, over $3 million in earnings, and near-unmatched consistency, Nitrogen arrives at Keeneland with far more than a single race on the line:she has the opportunity to solidify an all-time legacy.
