The last time Testashadow raced over 1500 metres at Rosehill, the Gary Portelli-trained gelding won the Group Three Festival Stakes.

That December win is Testashadow's most recent and Portelli believes the rising seven-year-old's chances over the course and distance in Saturday's Listed Winter Challenge hinge on how much a seemingly tough last-start run has taken out of him.

Testashadow goes into the Winter Challenge after finishing midfield in the Civic Stakes (1350m) four weeks ago before fading to finish second last in the Winter Stakes (1400m), both at Rosehill.

Portelli says Testashadow had not shown signs that the Winter Stakes run had taken any toll on him, but race day will be the telling factor.

"I think if you put a line through his last run you'd probably have him pretty competitive with a lighter weight and drawing well," Portelli said.

"He's in good order and looks good and is ready to go, but in that last run he was off the track and circling them from a long way out and it was awful to watch.

"You just knew at some point he was going to capitulate in the straight and he did.

"He has come through the run well and we're hoping he's back to his best."

The winner of eight of his 44 starts and earnings of more than $1.3 million, Testashadow has barrier five in the 17-horse Winter Challenge field which Portelli believes should give him every chance to enjoy a suitable run.

Testashadow was at $23 on race eve, with last-start Winter Stakes runner-up Invinzabeel the $4.20 favourite.

"I just wish he had an easier run last start," Portelli said.

"If he'd had a better run last start and hit the line strongly, you'd go there pretty confident he's going to be right in it.

"But you just don't know whether that tough run did take anything out of him.

"The only way we're going to know is on race day."