A fired-up Glen Boss was adamant Superium should have been declared the winner of the Up And Coming Stakes after the horse lost the race in the stewards' room.

Superium was first past the post by a head over True Detective but the latter's jockey James McDonald protested, arguing Superium shifted out over the final 50 metres and made contact with True Detective, causing McDonald to stop riding and costing his mount victory.

Boss also stopped riding and endeavoured to straighten his mount, in line with the rules of racing.

But unhappy with the decision by stewards' to overturn the result, the three-time Melbourne Cup-winning jockey questioned whether he should have maintained his vigour.

"I should have ridden the horse out to the finish, shouldn't I?" Boss said to chief steward Marc Van Gestel.

"It's a joke."

Van Gestel later summoned Boss back and questioned him about his comments, telling the jockey he was overheard by another steward to declare "it's a f****** joke" as he headed back into the jockeys' room and whether such conduct was appropriate.

"I've just got an opinion like you do," Boss replied.

Stewards fined Boss $1000 for the outburst with Van Gestel telling the jockey his behaviour seemed out of character.

Boss responded that he was confused by the stewards' interpretation of the incident as he felt True Detective had a chance to beat Superium but couldn't.

"I was confused and I reacted," Boss said.

The hoop pleaded guilty to the improper conduct charge and accepted accompanying fine.

The stewards' decision to uphold the protest delivered Chris Waller his first victory in the Up And Coming Stakes (1300m).

Sydney's premier trainer says True Detective is a work in progress and while the colt is nominated for the Group One Golden Rose, Waller is lukewarm on heading to the feature.

"Probably not the Golden Rose but I think he can measure up against the better horses at some stage of his three-year-old year," Waller said.

"He's still very green and he'll eventually end up racing with blinkers on but he's not ready for the yet."

Waller also claimed third spot with Lucicello and said she would be given a short break and return for a two-start campaign later in the spring.