The Alexandra Park heat will be light on numbers because Tim Butt and Mark Purdon's open-class teams have been campaigning in Australia, while horses who can't realistically win the final have been pulled out by their trainers.
A condition of the series was that if a horse made the final and didn't contest it they would face a 12-week stand-down from racing. That was enough to see pacers like Pembrook Benny, Jarcullembra and Easy On The Eye pull out so they could concentrate on the Auckland Cup carnival, run the same week as the Sydney final.
Interdominion officials have announced two horses from the Auckland heat will be invited to the final, while they will also retain one wild card entry over the five heats.
While a two-out-of-three chance of making the final sounds pretty good for the three Alexandra Park contenders, they have more at stake than most contesting the series.
All three - Sir Lincoln, Terror To Love and Gold Ace - are stallions with multiple group one wins in New Zealand.
But they are yet to shine in the important Eastern States of Australia.
Winning the Interdominion on what will be the biggest day of harness racing in Southern Hemisphere history could be worth millions in future service fees, not to mention the winning stake.
Three-horse races can be notoriously tricky, especially as once settled into single file the horse racing last is going to have to come race parked as the other pair, only needing to run first or second, can await the passing lane. In that scenario, the leader can probably control the tempo of the race, making it hard on the last horses, especially in a 55-second last 800m.
Of the three, Terror To Love is the one with the least to lose this Saturday because as the series favourite if he was beaten in a tactical battle he would more than likely be invited as the wild card.
He has drawn barrier two of the three, with Gold Ace (ace) and Sir Lincoln (three) either side of him.
The latter pair have blazing gate speed so Terror To Love could find himself having to come from last.
That will make a fascinating battle of tactics and gate speed on a night when harness racing enters a new and controversial era.
Gold Ace confirmed his place in the heat after pleasing trainer Steven Reid in a beach workout on Sunday.
The 5-year-old has been fighting a quarter crack so Reid allowed him to miss last Saturday's Alexandra Park workouts.
"But he worked great on the beach and the quarter crack is getting better all the time," said Reid.
"He will be right for the heat and I am confident by the time we get to the final it won't be an issue."
The biggest shock was when Victoria Cup winner Caribbean Blaster was found to be suffering from a minor virus on Sunday.
His trainer Andy Gath was much happier with the 5-year-old yesterday and with a good draw he will still start favourite in the Victorian heat at Melton. His arch-rival Smoken Up faces a horror draw there at one on the second line, with Bitobliss drawn the widest.
Hunter Cup winning Kiwi pacer Mah Sish will be red hot in the second supplementary heat at Menangle and should cruise into the final.
Interdom bosses upset some by ranking the heats with the main Sydney heat as the strongest, meaning the first four home there get final invites.
