Jockey Mark Zahra is in an awkward position riding against his Melbourne Cup mount Alcopop who needs to win Saturday's Group Three The Lexus Stakes to get a start in next Tuesday's big race.Zahra accepted the Lexus ride on the Peter Snowden-trained Purple before Alcopop's trainer Jake Stephens switched Cup lead-up races from the Mackinnon Stakes to the Lexus minutes before acceptance time on Wednesday.Blake Shinn is the replacement rider on Alcopop in the Lexus but Zahra is the frontrunner to ri

Jockey Mark Zahra is in an awkward position riding against his Melbourne Cup mount Alcopop who needs to win Saturday's Group Three The Lexus Stakes to get a start in next Tuesday's big race.

Zahra accepted the Lexus ride on the Peter Snowden-trained Purple before Alcopop's trainer Jake Stephens switched Cup lead-up races from the Mackinnon Stakes to the Lexus minutes before acceptance time on Wednesday.

Blake Shinn is the replacement rider on Alcopop in the Lexus but Zahra is the frontrunner to ride the six-year-old in the Cup if he makes the field.

The Lexus winner is exempt from the ballot and Purple is the only one of the 14 runners not paid up for the Cup.

Zahra warned that Purple could be the blowout horse for all the Melbourne Cup contenders needing to win The Lexus.

"If the track is going to be wet then she is in with a great chance," Zahra said.

"I think up to 2500 metres suits her. She is quite dour."

Zahra rode Purple last start when she looked beaten at the top of the straight and flashed home on heavy ground to finish second to Ginga Dude in the Group Three David Jones Cup (2000m) at Caulfield on October 16.

"It was a funny sort of run the other day," Zahra said.

"We wanted to go forward and she probably didn't have the speed we thought she did."

He said she was "gone" twice in the race and didn't find her feet until the race was over.

"Her last 50 metres was amazing," he said.

Zahra will have mixed feelings if Purple beats Alcopop but is focused on winning the Lexus.

"I hope Purple wins but if Purple can't win let's hope he (Alcopop) can win so he can get into the Cup field," he said.

Stephens said he made a late call to run Alcopop in the Lexus instead of the Mackinnon.

"I really wanted to run him over 2000 metres and not the 2500 metres but looking at the Lexus it is an easier race and the field isn't as big as I thought it would be," Stephens said.

The five top qualified Melbourne Cup runners are engaged in the Mackinnon including dual Cox Plate winner So You Think, Caulfield Cup winner Descarado and last year's Melbourne Cup winner Shocking.

With 47 horses paid up for the Cup and only 24 spots, the Lexus contest will be a highlight of Flemington's Derby Day meeting.

The only Lexus runners assured of a Melbourne Cup start are Once Were Wild (16th) and Jessicabeel (23rd).

Bart Cummings decided against backing up Precedence after last week's Moonee Valley feature win despite being 26th in order of entry.

Lexus runners Red Ruler (25th), Mourayan (27th), Herculian Prince (28th), Alcopop (29th), Linton (30th) are queued up looking for a Cup berth.

Geelong Cup runner-up Moudre (38th), Maluckyday (40th), Cedarberg (41st), Count Encosta (44th), Stanstill (45th) and Gothic Crown (47th) are other Lexus starters.

Weather could be a major factor with 50mm of rain forecast for Saturday.

Stephens said he hadn't ruled out scratching Alcopop from Derby Day if the track became badly affected.

"If it is too bad we may not run," Stephens said.

"We don't want to screw him up just for the sake of it.

"If he doesn't make the Cup, he doesn't make it."