'It wouldn't be a given who Ryan would ride' - Aidan O'Brien nominates his main Derby contenders as big Constitution River decision awaits

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Constitution River's Derby target remains in the balance – but Aidan O'Brien said sending him to Epsom would give Ryan Moore a headache over which horse to ride.

The pecking order for the powerful operation's Betfred Derby team is up in the air, with O'Brien nominating Chester Vase winner Benvenuto Cellini and Pierre Bonnard as his most likely representatives, but adding that a decision had not yet been made regarding Constitution River, who could tackle the Prix du Jockey Club a week earlier.

Benvenuto Cellini and Constitution River advertised their credentials in sparkling fashion at Chester last week, each securing emphatic wins, while Pierre Bonnard, who was the ante-post favourite for the Derby throughout the winter, suffered his second defeat of the campaign when narrowly denied at Leopardstown on Sunday.

Ante-Post Pricewise on the Derby:

• 'There's every chance he'll improve a lot' - Tom Segal has a 25-1 fancy for the Derby 

"We're looking at Benvenuto Cellini and Pierre Bonnard for Epsom," said O'Brien. "Constitution River could possibly go to France, as could Montreal and Hawk Mountain, but nothing is in stone."

Given Benvenuto Cellini landed the Vase over a mile and a half and O'Brien is confident that Pierre Bonnard will relish stepping up in trip, the door remains open for Constitution River to remain at a mile and a quarter and go to Chantilly.

"Constitution River went to Chester as we knew he could be an Epsom or a French Derby horse," he explained. "We were happy that it was a mile and a quarter, in case he was going to go to France. The only thing is that if he is going to France, he's only gone left-handed. But we felt he looked very different going through all his work and looked very good last year. We were hoping and expecting to see that at Chester. 

"He's one of these mile-and-a-quarter horses who could get a mile and a half, but you couldn't be sure. If you're riding him over a mile and a half, you'd be riding him patiently. He has a lot of speed and class."

On his other two candidates, he added: "Benvenuto Cellini has speed and class too and a big open stride. You'd be surprised if he didn't get a mile and a half but you would be surprised if he got much further. We think Pierre Bonnard will step up again after Sunday and is going to get a mile and a half and could get further."

Derby power rankings:

Has Monday's news from Ballydoyle swayed who is in pole position to win the Derby? Our power rankings reveal all 

Benvenuto Cellini has hardened into 5-2 favouritism for the Betfred Derby since an authoritative display at Chester, where he beat stablemate Proposition by four and a quarter lengths. 

However, O'Brien believes stable jockey Ryan Moore would have a very difficult decision to make if Coolmore decided to roll the Epsom dice with Constitution River, who was similarly impressive last week when powering seven lengths clear of Generic.

Constitution River working at Ballydoyle on MondayCredit: Patrick McCann (racingpost.com/photos)

"Ryan would have to find it hard to get off Benvenuto Cellini but I'd imagine if Constitution River went, he could get off him," said O'Brien. "It definitely wouldn't be a given [that he'd ride Benvenuto Cellini in that scenario], Ryan would think a lot about that."

'I know Benvenuto Cellini is a shorter price but Pierre Bonnard is going to step up'

Pierre Bonnard improved plenty for his Ballysax reappearance when a short-head second to James J Braddock in the Derby Trial at Leopardstown on Sunday and O'Brien is confident another big step forward is imminent at Epsom, despite the early-season favourite being pushed out to as big as 16-1. 

Action and Ballysax winner Christmas Day could also be thrown into the mix, depending on how they fare in the Dante at York on Thursday.

"Pierre Bonnard was a massive, big horse last year and we purposefully let him get as big and as strong as we could over the winter because we didn't want him to turn into a shell early," said O'Brien. "We felt we had to run him the first day at Leopardstown and the race went a bit wrong and he needed it. Because of where he was, we couldn't go and attack into him and have him really ready for Sunday as he wouldn't carry on to the Derby. 

"We stripped him back a bit more for Sunday and the pace was probably too slow, but he still ran very well. We think that he would step up big-time next time over a mile and a half. I know Benvenuto Cellini is a shorter price, but Pierre Bonnard is going to step up."

Betfred Derby, Epsom, June 6
Betfred: 9-4 Benvenuto Cellini, 5 Constitution River, 10 Maltese Cross, 12 Christmas Day, 14 Hawk Mountain, Pierre Bonnard,16 Bay Of Brilliance, 20 Ancient Egypt, Morshdi, James J Braddock, Saxon Street 25 bar

Read more:

Has Monday's news from Ballydoyle swayed who is in pole position to win the Derby? Our power rankings reveal all 

'He's a gorgeous horse' - Aidan O'Brien and Ryan Moore enjoy yet another Epsom trial success with Constitution River 

'He's ticked a box to go to Epsom' - all systems go for Derby with Benvenuto Cellini following dominant Vase victory 

The surprising lesson from Aidan O'Brien's double in Chester's Classic trials on Wednesday 

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