Stallions such as Zed, Ekraar, Nom de Jeu, Zacinto and others will leave horses who won't be disadvantaged by wet tracks, whereas some of the speedier stallions will leave horses who fail to let down on the bogs.
It is not exact science and to a degree trainers shield punters from abject wet track failures by not having them in work in the depths of winter.
But after three months of racing was lost to lockdown there may be a few better track horses floating around at the moment than there would be during a normal winter.
"I have tried to avoid that by making sure the horses I have racing at the moment are true winter horses," says Tiley, who trained two winners at the Pukekohe comeback meeting two weeks ago.
Those were ridden by his young stable apprentice Callum Jones on a glorious debut day.
Jones has another reason to celebrate today as his first day riding at Ellerslie will be his 18th birthday and Tiley likes what he sees of the youngster in the saddle.
"He has good balance. He has done a lot of surfing and that has helped his balance. So he has a future."
Jones will ride Pukekohe winner Double Happy (R9, No1) where his 4kg claim will be crucial but Tiley warns punters to be careful of second-up syndrome.
"He is a good handicapper in the making who can win a nice race next season but often horses like him will go great fresh but be a bit more dour next start."
Tiley rates two of Jones' other rides, Macushla (R2, No7) and Lupelani (R10, No2) as his best two chances today.
"The filly [Macushla] goes well enough to win a maiden pretty quickly while Lupelani will be better for his last start second and she has to go close."
Today's other domestic meeting is at Riccarton in Christchurch.
Best for the day
Tony Pike, trainer: "Divine Dive (Ellerslie R1) has tightened up well since the fresh up run, working well and should go close."
Matt Cameron, jockey: "Red Beach (Ellerslie R9) trialed well, has been working well since and likes the wet."
Nigel Tiley, trainer: "Lupelani (Ellerslie R10) will be better for that last start second, gets the claim and she is flying."
Michael Pitman, trainer: "Turncoat (Riccarton R8) would have won last start had he run straight. We have made a gear change and he claims 4kg."