The Michael and Matthew Pitman-trained Enzo's Lad pipped Ferrando to win by a nose in a result that took several minutes to be announced.
“That's unbelievable,” McNab said.
“They didn't call it and didn't call it and I didn't want a dead-heat.
“I just threw my gear everywhere, it's just unreal.
“What a horse. I was coming down just before he got over the junction and I was just bolting but then he stumbled a bit.
“He mustered again real quick and when I got out, I thought ‘here goes the big boy'.
“I felt like I was going to get past, but I was running out of time – that's just unreal.”
Michael Pitman was overjoyed and surprised Enzo's Lad was at 30-1 in the 1200m-dash.
“We went into the race with a lot of confidence as he went massive at his last start,” he said.
“I was annoyed last year when he wasn't a candidate for sprinter-miler of the year as people had described that field as the best in twenty years.
“He's come out today and beaten an even better field, so I think he deserves some sort of recognition for that.
“He might come back now and have a crack next year. If you only win one race a year, but it's a Group One, then it's worth racing horses.”