Anthony Cummings is keen to dispute the theory that winning streaks in the middle of summer have little relevance to what happens when the stakes are raised in the autumn.

Cummings' team is in tremendous shape heading into the serious part of Sydney's carnival, especially with Montaigne rated some chance of upsetting Press Statement in the Randwick Guineas.

But if Cummings is right, it might be a mare just out of restricted-class racing that could provide a stable highlight at Randwick on Saturday.

Rule The River returns in the Challenge Stakes, a Group Two sprint run at weight-for-age with the depth equal to any race on the Guineas card.

Trainer Gai Waterhouse will provide two of the favourites, English ($3.80) and Speak Fondly ($7), but Cummings isn't frightened to pitch Rule The River into a contest that is a crucial lead-up race to the Group One Galaxy at Rosehill.

"Saturday's race will give us a guide as to where she fits at that level," Cummings said.

"But if we get what we expect we'll go to the Galaxy."

Rule The River started her summer campaign with a first-up victory over 1100m at Canterbury and won three more races before her sequence ended with a minor placing in the Takeover Target Stakes.

Blake Shinn takes the ride from an inside draw with Rule The River rated a $17 chance.

Cummings also has unbeaten mare Flashing Speed resuming in the Wenona Girl Handicap.

Flashing Speed won her only starts in her first racing campaign and was put away after a city midweek win in October.

The Randwick trainer will also test Moqueen against Sydney's best two-year-old fillies in the Reisling Stakes.

A Hugh Bowman ride, Moqueen picked up late ground from the back of the field to be beaten less than a length when fourth to Omei Sword at Rosehill last week.

"She's come out of her race in very good shape," Cummings said.