James McDonald aboard Generation

James McDonald aboard Generation (inside), who held off Scissor Step (Image: Racing Photos)

Generation win a tonic for JMac

James McDonald may have had an awful start to Cox Plate Day but his mood quickly improved after partnering favourite Generation to victory in the Group 3 Red Anchor Stakes.

McDonald said he was in shock at 7:32am on Saturday morning when he received the first of many messages that the horse he thought would bring him his first Cox Plate had been scratched due to an elevated temperature.

"It felt like the rug had been swept straight from underneath you," he said of the moment when he heard of Zaaki's withdrawal.

"It just shows in racing that a week is a long time. We were on top of the world and then 7:32 (am) I got the phone call and it hurt a little bit, to be honest.

"I kept checking the scratchings to see if it was real. But that's racing. He'll live to fight another day and thank God, Annabel (Neasham) has another one (Mo'unga) in the race."

WATCH: Generation's Red Anchor Stakes win

As for Generation, who was sent out the $2.20 favourite and who did just enough to hold off a late-charging Scissor Step ($16), McDonald said: "Good, tough effort. A lovely colt who executed beautifully and he got the job done.

"If I had ridden him before I probably would have waited a little bit longer but he had a good turn of foot and was tough and towards the end the better he fought. Nice horse."

Co-trainer Dave Eustace said Generation took a while to get over his last-start defeat at The Valley seven weeks ago.

"Great to see. The last race took a fair bit out of him and we decided to give him a little bit of a freshen up. He's had a bit of time between runs. He just needed to fill up and put a bit of weight back on," said Eustace, who trains in partnership with Ciaron Maher.

"The team down at the beach at Balnarring have done a great job and he had a nice gallop here at The Valley. He's still progressing."