Sincero has confirmed his class with a fighting victory in the Group One George Main Stakes at Rosehill.
The margin on the line was a neck with Triple Elegance another three-quarters of a length third.
It was the first Group One success for O’Brien who had to watch from the sidelines when Sincero won the Stradbroke Handicap in June with lightweight jockey Jason Taylor aboard.
With the weight-for-age scale in O’Brien’s favour in the George Main, he took full advantage.
“When Ilovethiscity got a neck in front I knew we had a fight,” O’Brien said.
“But he loves a fight.”
Trainer Stephen Farley has earmarked the Epsom Handicap and Cox Plate as further targets for Sincero this spring.
Sincero is the reigning favourite for the Epsom Handicap at Randwick on October 1 in which he has 56.5 kilograms which is in O’Brien’s weight range.