Diamond Necklace's stunning Nassau Stakes win at Glorious Goodwood has catapulted her into the Prix de l'Arc de Triomphe conversation, with bookmakers now offering 10-1 odds for the October showpiece. The Aidan O'Brien-trained filly extended her unbeaten record to six races with a commanding two-and-three-quarter length victory, cementing her status as a top contender in horse racing betting markets.
Diamond Necklace's Dominant Goodwood Performance
Under jockey Ryan Moore, Diamond Necklace made light work of a competitive Nassau Stakes field at Goodwood on Thursday. After a narrow nose victory in the French Oaks at Chantilly in June, this performance was far more emphatic. She cruised past second favourite Friendly Soul inside the final quarter-mile, showcasing the acceleration that has made her one of Europe's most exciting fillies.
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This was her fourth Group One victory, and her trainer Aidan O'Brien was full of praise: "Diamond Necklace is a lovely filly who has danced every dance." The win has naturally led to speculation about her next target, with the Prix de l'Arc de Triomphe at Longchamp emerging as a tantalising possibility.
Arc de Triomphe Odds and Contenders
Following the Goodwood success, Diamond Necklace is now the 10-1 third-favourite for the Arc, behind last year's winner Daryz and O'Brien's star colt Constitution River. While her stamina for the 12-furlong trip remains untested, history is on her side – female runners have won nine of the last 15 Arcs. The bookmakers' confidence is reflected in her odds, but the question remains whether she can handle the step up in distance.

O'Brien remains cautious but optimistic: "It is possible [the Prix de l'Arc de Triomphe]. I don't know how far we ask her to go, but the next run will tell us." Her immediate options include the fillies' race at Deauville in August or an Arc trial at Leopardstown in September.
Comparing Diamond Necklace's Profile to Recent Arc Winners
| Horse | Arc Win Year | Key Prep Race | Odds Before Arc |
|---|---|---|---|
| Diamond Necklace | 2025 (projected) | Nassau Stakes (Goodwood) | 10-1 |
| Daryz | 2024 | Prix de l'Arc de Triomphe Trial | 5-1 |
| Enable | 2017, 2018 | King George VI & Queen Elizabeth Stakes | 4-1 |
| Treve | 2013, 2014 | Prix Vermeille | 6-1 |
As the table shows, many recent Arc-winning fillies and mares used a strong trial race to build momentum. Diamond Necklace's Nassau victory fits that pattern, but she will need to prove her stamina in a longer trial to convince punters.
Key Takeaways from the Nassau Stakes
- Diamond Necklace remains unbeaten in six career starts, with four Group One wins.
- Her 10-1 Arc odds make her a live contender, but stamina doubts persist.
- Aidan O'Brien will decide her next run based on how she trains, with Deauville or Leopardstown as likely options.
- Constitution River remains the stable's primary Arc hope, with a York International Stakes appearance next.
- Female dominance in the Arc (9 of last 15) adds to her appeal.
What's Next for Diamond Necklace?
The immediate future for Diamond Necklace is uncertain, but the signs are positive. O'Brien has a wealth of options, and her next start will be crucial in determining whether she heads to Longchamp. If she can overcome the stamina question, she could be a serious player in October.
For bettors, the 10-1 price offers value, but it's wise to wait for her next run before committing. Keep an eye on the Deauville meeting in August and Leopardstown in September for clues.
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Stay tuned to GrandGoldman.com for the latest horse racing betting tips and analysis as the road to the Arc heats up.