The headline moment came on 4 December 2021, when O'Sullivan won a top-level race at Aintree — one of the most storied venues in British racing. Landing one of the sport's biggest prizes in your debut year as a trainer is not something that happens by accident. It announced O'Sullivan as someone worth watching, not just a name filling out an entry list.
The numbers get more interesting when you dig into specific conditions. On very wet, muddy ground — the kind of heavy going that turns a racetrack into a test of raw stamina and toughness — his runners win 15% of the time, 6 victories from 39 races. That's nearly 1 in every 6 starts in the most demanding conditions. It suggests O'Sullivan knows how to prepare horses that genuinely thrive when it's miserable out, which is a skill in itself.
His most productive partnership with a jockey is with Danny Gilligan, who has ridden 67 horses for the yard and won on 9 of them — a win rate of 13%, or roughly 1 in every 7 rides. That is meaningfully better than the yard's overall average, and when a trainer keeps booking the same jockey at that kind of return, it tells you the relationship is working. Then there is Switch From Diesel, the horse that stands apart from everything else in the yard — 4 wins from just 13 races together, which is a genuinely impressive conversion rate and the kind of partnership that makes everyone's day when the name appears on a racecard.
Forty winners a season, a top-level scalp already on the board, and a yard that clearly knows what it is doing in the mud. O'Sullivan is still early in his training career, but the foundations look solid.
| Course | Races | Wins | Win rate |
|---|---|---|---|
| Naas | 50 | 2 | 4% |
| Dundalk | 41 | 5 | 12.2% |
| Punchestown | 41 | 4 | 9.8% |
| Fairyhouse | 27 | 2 | 7.4% |
| The Curragh | 25 | 2 | 8% |
| Gowran Park | 19 | 2 | 10.5% |
| Wexford | 19 | 1 | 5.3% |
| Limerick | 18 | 1 | 5.6% |
| Galway | 16 | 3 | 18.8% |
| Navan | 16 | 3 | 18.8% |
| Roscommon | 16 | 2 | 12.5% |
| Leopardstown | 15 | 2 | 13.3% |
| Listowel | 12 | 1 | 8.3% |
| Cork | 12 | 0 | 0% |
| Tramore | 11 | 2 | 18.2% |
| Tipperary | 11 | 1 | 9.1% |
| Kilbeggan | 10 | 1 | 10% |
| Thurles | 10 | 1 | 10% |
| Killarney | 10 | 0 | 0% |
| Downpatrick | 9 | 1 | 11.1% |
| Ballinrobe | 8 | 2 | 25% |
| Down Royal | 8 | 1 | 12.5% |
| Clonmel | 7 | 1 | 14.3% |
| Sligo | 7 | 0 | 0% |
| Bellewstown | 5 | 0 | 0% |
| Newcastle | 2 | 0 | 0% |
| Haydock Park | 2 | 0 | 0% |
| Aintree | 1 | 0 | 0% |
| Kelso | 1 | 0 | 0% |
| Market Rasen | 1 | 0 | 0% |