GAI Waterhouse concedes the wet track might dull Thinkin’ Big’s speed but she is adamant it won’t prevent the star colt from claiming Sydney’s final Group 1 race of the year, the $500,000 Spring Champion Stakes (2000m) at Royal Randwick.

“If we are racing on a heavy track It might take away from Thinkin’ Big’s brilliant sprint, his turn of foot,’’ Waterhouse said. “But in the Gloaming Stakes last start he proved himself the dominant three-year-old the way he won that day.

“He is a very happy horse, he’s easy to train, loves to get on with the job, he’s a very straightforward and professional horse. He’s the one they have to beat.’’

TAB Fixed Odds prices assessors agree with Thinkin’ Big rated the $3.40 favourite to score his fourth win from just five starts.

Thinkin’ Big is coming into the Spring Champion Stakes off the traditional lead-up race, the Gloaming Stakes, where he was too strong for Tarka and Irukandji.

In the last six years, there has been four horses complete the Gloaming Stakes-Spring Champion Stakes double — It’s A Dundeel (2012), Complacent (2013), Vanbrugh (2015) and Ace High (2017).

Waterhouse, who trains in partnership with Adrian Bott these days, is aiming for a record-equalling fifth win in the classic after her wins with Nothin’ Leica Dane (1995), Magic Of Sydney (1996), Platinum Scissors (2002) and Hampton Court (2014).

Her late father, the great Tommy Smith holds the training record with five wins.

Thinkin’ Big’s paternal grandsire is Nothin’ Leica Dane, while the colt’s sire, High Chaparral, has been represented by three Spring Champion winners — Monaco Consul (2009), It’s A Dundeel (2012) and Ace High (2017).

“This colt has a wonderfully stout staying pedigree,’’ Waterhouse said. “Full credit to his owner, Peter Dunn, to be game enough to breed a superior stayer when there is so much emphasis on sprinters in this country.’’

Waterhouse confirmed Thinkin’ Big was on a Victoria Derby trail along with stablemates Sydney Blue and Transact.

Golden Pendant winner Shumookh is also trying to continue her rich vein of form in the Group 3 $160,000 Angst Stakes (1600m).

Shumookh led and fought off Champagne Cuddles at Rosehill last start and Waterhouse was adamant the mare would run 1600m today “with her eyes shut”.

“The thing about Shumookh, and Thinkin Big for that matter, is that they are very fit and they have won in these wet conditions,’’ Waterhouse said.

“Shumookh is a beautiful mare and was very gutsy in the Golden Pendant. She doesn’t know the meaning of defeat.

“I know this a mare who is very close to (owner-breeder) Nasser Lootah’s heart.

“He bred and raced her dam, Shamekha, and she was an outstanding mare.

“We won three Group 1 races with her, including the T.J. Smith Stakes. Shumookh is the best of her progeny, only lightly raced but with so much ability.’’

Waterhouse said she planned to have Shumookh join Thinkin’ Big at Flemington on Derby day, targeting the Myer.

At Flemington on Saturday, Waterhouse has a strong team — including Cup hopefuls Hush Writer and Northwest Passage in the Group 3 $300,000 The Bart Cummings (2500m). Hush Writer, the Japanese-bred former French stayer, has been improved by three Australian starts — including his third to Haripour in the Listed Harry White Classic at Mornington last week.

Northwest Passage won the Tasmanian Derby and Torney Cup last year before suffering a leg injury but has been improved by three runs off a long spell.

“Hush Writer is still learning his trade, still learning what racing in Australia is all about, but he is a very promising horse,’’ Waterhouse said. “Northwest Passage is a lovely horse, bred to be a nice stayer, and is getting back to his best now.’’

Waterhouse is also hopeful of a return to form from dual Group 1 winner Global Glamour in the Group 2 $200,000 Blazer Stakes (1400m).

The mare ran only ninth to Winter Bride when resuming in the How Now Stakes two weeks ago but has done well since, according to her Hall of Fame trainer.

“She looks good, her coat is coming right and I’m happy with her,’’ Waterhouse said. “I’m hoping, back to Flemington, she will run well.’’