The three-year-olds are among the top fancies for Saturday's Group One George Ryder Stakes but connections of El Roca and Eurozone concede their colts need to raise the bar.

The duo takes on a field high in quality and depth headlined by Boban, Red Tracer, Streama, Gordon Lord Byron and the up-and-coming Terravista.

Eurozone has managed a top-four finish at his past three starts but is still searching for his first win of the autumn.

James Cummings concedes the colt has lacked a knock-out punch and together with grandfather and co-trainer Bart, he has made two important changes.

Eurozone will wear blinkers for the first time at Rosehill and have a new jockey in Jim Cassidy.

"His form has been consistent in Group One company in his three runs but he hasn't won," James Cummings said.

"And he is taking on Boban, Gordon Lord Byron and a stack of weight-for-age horses when he has just been running holes in three-year-old company.

"But with the blinkers on and Jimmy Cassidy on, there's a big chance of him improving.

"Glen Boss rode him perfectly but for the past week Jim has been driving to the track of a morning as confident as any other jockey."

The stable has reported Eurozone was galloped on when a last-start third in the Randwick Guineas but scans showed no damage and he missed no work.

Cummings reassured punters there were no issues with the colt.

"If there were he certainly wouldn't be running," Cummings said.

El Roca has had issues of his own after missing a lead-up run in the Hobartville Stakes due to a pre-race treatment mix-up.

His program was rejigged and the colt went into the Randwick Guineas on a seven-day back-up, finishing a narrow second to Dissident.

"His preparation was a little interrupted going into the Randwick Guineas but I make no excuses, he was beaten on his merits," jockey Hugh Bowman said.

"He's on track for a big performance but he's going to have to lift because he's going up in class."

Red Tracer is the new George Ryder favourite at $3.20 following a track downgrade to heavy on Thursday, ahead of stablemate Boban ($4.20).

El Roca and Eurozone are next at $8 and $9 respectively.