Requisition (7-2) made all to win the Anne Brewster Memorial Loughbrown Stakes at the Curragh.
Aidan O'Brien's Invincible Spirit colt was the lesser-fancied of the two Ballydoyle runners with Nephrite sent off the 4-9 favourite under Joseph O'Brien.
However, while travelling well for much of the contest, Nephrite's response was limited when asked to quicken inside the final furlong.
The front-running Requistion was a length-and-three-quarters ahead of runner-up Coolnagree (12-1) at the line, with Nephrite having to settled for third.
Ladbrokes went as short as 8-1 about Nephrite for the 2,000 Guineas pre-race, but have now doubled his odds to 16s with stablemate Camelot cut to evens favourite.
O'Brien senior said: "He progressed well from last year. He got a mile well in Galway when he won his maiden.
"Looking at him you wouldn't think he'd get a mile. He is a very straightforward horse to train."
Of Nephrite, the trainer said: "He won his maiden here over six furlongs and he wasn't sure to get a mile. He has lots of speed but he was just found out on the ground."