Atlantic Jewel faces her acid test in Saturday's Group One Underwood Stakes.

And her jockey Michael Rodd is looking for the unbeaten star to answer the challenge like she has in every start so far.

Rodd has unwavering confidence in Atlantic Jewel's ability which has netted nine wins from as many starts but says the step up to 1800m at Caulfield against 10 Group One winners represents her biggest challenge.

"She has won over 2000 metres before in the Wakeful and she just sort of cantered around that day. It's a totally different ball game with these quality horses that she's racing," Rodd said.

"This is her acid test. If she comes through it and does win and is impressive then obviously the Cox Plate is well in her grasp and we'll be a lot more confident.

"But tomorrow there's still some questions to be answered."

Atlantic Jewel is a $1.60 favourite to become the first mare since Tristarc in 1985 to win the Underwood and Rodd believes the tempo of the race will be a key to the outcome.

Rodd won't be concerned if Atlantic Jewel is the leader but he expects some of her rivals, especially It's A Dundeel, to charge home.

"It looks like she (Atlantic Jewel) should get a nice run up on the speed there and if it turns into a sprint home they won't see which way she goes," Rodd declared.

"But if it's a staying test, then there might be some question marks."

Atlantic Jewel scored an effortless victory in the Stocks Stakes last Saturday and Rodd believes the back-up is no concern nor is the possibility of a slow-rated track.

The hype around Atlantic Jewel's unbeaten streak continues to gather momentum and Rodd wants to enjoy the ride.

"We're just taking it as it comes and trying to enjoy ourselves as well because I might never get on a horse like this again in my whole career," he said.

Puissance De Lune is second favourite but his jockey Glen Boss doubts the Melbourne Cup favourite can topple Atlantic Jewel on Saturday despite expecting him to run well on his way to his major spring missions.

"As I see it as I stand right now I probably couldn't beat her (on Saturday)," Boss said.

"But my horse is looking for bigger goals further down the track."

Boss, however, says it is too early to call Atlantic Jewel a champion.

"She's got an amazing record and has got the platform to build to be a champion but it's very premature to start calling her a champion at this stage because she's got to be winning majors and beating very good horses," he said.

"But she's on the way, that's for sure."