A middle-distance race is not Bjorn Baker's first choice for Harpo Marx but he is hoping a rain-affected track can help his chances.

The European import will tackle the ANZ Bloodstock News Handicap (2000m) at Rosehill having worked his way through the grades during the summer.

He made it three wins from his past four starts when he chased down Vadiyann over Saturday's course and distance at his most recent appearance but will meet the Tulloch Lodge galloper two kilos worse when they clash again.

Baker would ideally like Harpo Marx to be rising in journey but says a rain-affected track could make Saturday's race more of a stamina test.

"He's going super. It is another step up again on Saturday but a bit of rain around might help him," Baker said.

"It might just make the track a bit more demanding."

In-form jockey Rachel King has been the regular rider of Harpo Marx this campaign and will again be in the saddle.

Baker has no grand plans at this stage and believes the five-year-old will be an even better horse next preparation.

"He's a horse we are really keen on," he said.

"We will just try to win races, that's the aim. We will take it one step at a time but he is going well at the moment, although he is better over further."

Baker will have up to seven runners at Rosehill and both Canasta and Frosty Rocks are early favourites for their respective races.

Harpo Marx ($6) is also high in commission in an open betting race.