Jockey Mark Zahra believes an important gear change might be the edge Shoals needs to win the $500,000 Thousand Guineas.

Shoals lost her unbeaten record when second to Booker in the Thousand Guineas Prelude over 1400m at her fifth career start last Sunday week, but Zahra took positives out of the closing stages of the race.

The in-form jockey tested the filly in blinkers in a gallop at Flemington on Tuesday morning before giving trainer Anthony Freedman the thumbs-up to apply them for Saturday's Group One race over 1600m.

The blinkers will replace her normal winkers.

"She was sharp enough but relaxed enough," Zahra said.

"It's always a risk going up in trip and putting blinkers on but I reckon she just needed something extra if we think we're a chance of winning, which we've done.

"She'll wear the blinkers and I reckon she'll run really well."

Sydney filly Alizee has unleashed a powerful finishing burst to win the Tea Rose Stakes and Flight Stakes at her two most recent starts and is the $2.20 Thousand Guineas favourite.

Shoals is at $4 ahead of Booker ($6.50).

While Alizee has proven herself at 1600m, Shoals and Booker are yet to do so.

"The mile is going to be the biggest test for Shoals," Zahra said.

"She's been impressive over 1200 metres and then she had her first run at 1400 the other day and I thought she was good through the line.

"Catchy levelled up with me and I kicked and beat her for second which I reckon was a really good sign.

"With only eight runners it's going to make it a lot easier for her I reckon. She needs a soft run in transit to run the mile for sure."

Zahra rides Group One-winning filly Catchy in the $2 million Caulfield Guineas against the colts and geldings on Saturday with the filly's trainers David and Ben Hayes and Tom Dabernig to rely on Pure Scot in the Thousand Guineas.

Pure Scot flashed between runners late in the Edward Manifold Stakes last Saturday over 1600m to finish fourth after having difficulty obtaining clear running.