Aidan O'Brien hit the target for the first time at this year's Breeders' Cup meeting when George Vancouver struck in the Juvenile Turf at Santa Anita.
Ballydoyle's inmate was delivered to perfection by Ryan Moore to take this Grade One over a mile in some style.
Whereas George Vancouver had a dream passage towards the line, the Roger Charlton-trained Dundonnell endured a fractious journey and finished fourth under James Doyle. Noble Tune came home in second place, while Balance The Books was third.
Owner Michael Tabor, of the Coolmore triumvirate, said: "He's been waiting for this fast ground, and that really was the key.
"Everything's possible next season now. He's obviously a top-class horse and hopefully he'll go for all the big races."
Charlton was satisfied by Dundonnell's fourth-placed finish.
He said: "I was pleased. We all saw he ran very wide on the first bend, which took us by surprise, but James got him in a good position until he just faded in the last 200 metres.
"He had every chance, but on the day he wasn't quite good enough."
Ballydoyle's second string, Lines Of Battle, showed good early pace before drifting out of contention.
Jockey Richard Hughes said: "He got a good, early position from a tricky draw, but I didn't get home in the straight."