The horse scored the victory courtesy of a brilliant frontrunning drive by Dexter Dunn.
McKay had two runners in race 6 and was driving Gorilla Playboy, who finished 11th.
The horse's early gallop put him out of race contention and gave McKay a terrible view of the event.
The driver had only horses' rumps and dust in front of him as Dunn and his other stable runner were controlling the race tempo up front.
The further Playboy's Brother went, the further he got in front of the field.
Quite simply, the horse was in his happy place.
''He was just a happy horse out there today,'' Dexter Dunn said.
''He wanted to bowl along in front and I wasn't going to fight him.
''He did it easy.
''I did not even pull the [removable] hood and I could hardly pull him up after the race.''
So fast did Playboy's Brother want to run he set an Omakau track record.
His winning time of 3.20.4 for the 2600m standing start took 0.7sec off the previous record, set by Mon Richie at last year's meeting.
The removable gear was not needed when Dunn's brother John drove Tuapeka Trick to victory in race 5, either.
Dunn steered the Robert Dunn-trained 3yr-old to a two-and-a-quarter-length victory.
The win would serve as a confidence boost for the pacer, who had run good races against a line-up of classy 3yr-olds in his last four starts.
''If you look at his last four starts, except for Methven on the grass, they have gone some very fast mile rates,'' John Dunn said.
The horse would now target the upcoming two-day meeting in Nelson.
Dexter Dunn also combined with Hicori for an effortless victory once he gained clear racing room in race 3.
Dunn had a nervous wait for the passing lane as the leaders, Nadeen Franco and Like Ya More, went to war up front before the turn.
Once into the clear, he let the Regan Todd-trained pacer down for an easy win.
The trainer has the Southern Supremacy Stakes final as a long-term goal for the horse.
The 3yr-old had his early education with the Mark Purdon and Natalie Rasmussen stable, but his owners sent the horse to Todd so he could be trained on the beach.
''He just needed a bit of time and the owners thought he would benefit from the beach training,'' the trainer said.
''You are pretty grateful to get a horse like this through the gate.
''He is a very nice horse; he is another six months away from his best.''
Crusher Collins trotted to an emphatic victory in yesterday's second race for trainer Lyndon Bond and driver Nathan Williamson,
charging away to a massive 10 and a-quarter-length victory.
Williamson had the mare in front and out of trouble while chaos ensued behind her.
The favourite, Horse Of Course, was taken out of play by rival Still Eyre at the 1500m mark.
After galloping and looking out of the race, the first-starter put up a huge performance to finish third.
Horse Of Course was later promoted to second and Still Eyre was relegated to third.
