Scintillula (6-1) turned in a gutsy performance to defeat hot favourite Mars in the Group Three Jockey Club Of Turkey Meld Stakes at Leopardstown.
The Aidan O'Brien-trained Mars was stepping down in class after being campaigned at the highest level this term, claiming third in the St James's Palace Stakes and fourth in the Eclipse at Sandown last time as well as finishing sixth in the Derby.
He was sent off the 8-11 favourite for this nine-furlong heat and still looked to be travelling well on the heels of the pace-setting Scintillula, but when Joseph O'Brien gave him the signal to push on, Scintillula went with him and battled gamely on the rail for Kevin Manning.
Mars soon dropped away and that allowed Scintillula, who was making a swift reappearance having finished a close-up fourth in last weekend's Irish Oaks, to triumph by two and three-quarter lengths.
Winning trainer Jim Bolger said: "She's come right now and she's hardy. In the spring time she wasn't right. I thought we may have got a different result if we had made the running last Saturday."
The ground eased before the off after a sharp rain shower and Bolger admits it had been a worry.
"It was a concern but I was happy with the way she picked up," he said.
"We could look at the Give Thanks Stakes at Cork (August 6) for her."
Joseph O'Brien felt the change in ground had gone against his mount.
He said: "He hated the ground. I quickened to go upsides the winner but in the straight the ground is soft, he was all over the place and couldn't really get a hold of it. He's been running consistently well on good ground.
"He was on the bridle for the first five or six furlongs, but I knew my fate five furlongs from home. As soon as I let him down, he went nowhere."