Nitrogen Arrives at Oaklawn Ahead of 4YO Season

Florida-based dual Hall of Fame trainer Mark Casse said in November that he would send some of his best horses to Oaklawn Park for its 64-day split season that began Dec. 12, adding they would arrive in waves.

The latest wave washed ashore last weekend, carrying, among others, millionaire grade 1 winner Nitrogen , whose major spring objective is the $1.25 million Apple Blossom Handicap (G1) for older fillies and mares April 11 at Oaklawn, Casse said.

Casse had previously shipped grade 1 winners Sandman  and La Cara  to Oaklawn, then grade 2 winner Ewing  to continue preparations for major races this winter and spring in Hot Springs. Like Sandman, La Cara, and Ewing, Nitrogen had previously been based at Casse's training center in north-central Florida.

Assistant trainer Caden Arthur, who oversees Casse's Oaklawn division, said Nitrogen was vanned to Oaklawn and arrived around 7 a.m. CT Jan. 11.

"She looks great," Arthur said Jan. 13. "She's healthy right now and we're very excited for her 4-year-old campaign here at Oaklawn Park with her."

Casse said Nitrogen could launch her 2026 campaign in the $400,000 Azeri Stakes (G2) March 7. The Azeri is the final major local prep for the Apple Blossom. Both races are 1 1/16 miles.

A homebred for D. J. Stable (Jonathan and Leonard Green), Nitrogen is among three finalists for an Eclipse Award as North America's champion 3-year-old filly of 2025 after winning six of nine starts, including the Alabama Stakes (G1) at Saratoga Race Course. In her last two 2025 starts, Nitrogen finished second against older horses in the Spinster Stakes (G1) Oct. 5 at Keeneland and the Breeders' Cup Distaff (G1) Nov. 1 at Del Mar. Nitrogen logged workouts Dec. 31 and Jan. 7 at Casse's training center before shipping to Oaklawn.

Nitrogen, a daughter of Medaglia d'Oro , has an overall record of 6-4-2 from 12 starts and earnings of $2,046,604. Nitrogen is also a graded stakes winner on grass.

Arthur said Nitrogen was among six horses that arrived Sunday, increasing Casse's total to 28 on the grounds. The group, Arthur said, includes "a couple of non-starters," one being Equity , a 3-year-old colt from the first crop of millionaire multiple grade 2 winner Tacitus  . Equity is a half-brother to millionaire multiple group 2 winner Isolate .

Casse was maybe the biggest story of Oaklawn's 13-day Holiday racing season that concluded Jan. 4.

Casse won at a staggering 48% clip (11 of 23), highlighted by four stakes, and bankrolled $821,659 in purses. Casse also recorded five runner-up finishes and three thirds, meaning 83% of his starters finished in the top three.

Casse had starters in four stakes races and produced a 4-1-0 record, with Strategic Risk  and Silent Tactic  finishing first and second, respectively, in the $250,000 Smarty Jones for 3-year-olds Jan. 3.

Casse also won the inaugural $135,000 Astral Spa Overnight Stakes and $150,000 Year's End Stakes with Counting Stars  and the inaugural $135,000 Oaklawn Sports Overnight Stakes with Nerazurri .

"It's kind of unbelievable," Arthur said. "To be almost 50% (win percentage) in horse racing is crazy. Fifteen percent is pretty good, and to be at 50% to start the meet is unbelievable. Thanks to the horses, of course, and our whole team and the owners for this great start. Having some nice horses that fit here at Oaklawn Park definitely helps and we're just trying to take advantage of it and keep winning races and keep the horses healthy and sound."