Hardline's tilt at the Group One Coolmore Stud Stakes is unlikely after his failure at Doomben.

The Liam Birchley-trained three-year-old ran last in a Class 6 Plate at Doomben on Saturday with stewards to resume an inquiry into his performance later this week.

The winner of the New Zealand Karaka Million in January, Hardline won the first two starts of his campaign before Saturday's inglorious performance.

He missed the autumn with a hamstring injury but Birchley had been confident he was back to his best.

His jockey Damian Browne said Hardline was "crunched" on the first turn and was under pressure at the 600m.

"I didn't knock him about in the straight when he obviously couldn't run a place" Browne said.

Birchley said Hardline may have not been suited by the firm track but was still disappointing.

"I won't make any decision until I see how he pulls up in the next few days," Birchley said.

An initial vet's examination found no abnormalities with Hardline.

Stewards opened an inquiry into interference suffered by Hardline, Any Day Will Do and Sarisara on the first corner.

The Queensland stewards were kept busy after a rough-house day at Doomben during which three jockeys were suspended and another given a severe reprimand.

Brad Stewart copped his sixth careless riding suspension since May while apprentices Luke Dittman and Alannah Fancourt were both outed for 12 days and Luke Tarrant reprimanded.