'We don't know what his limit is' - Aidan O'Brien on his crack Goodwood squad

Aidan O'Brien is set to launch a three-pronged attack on the Sussex Stakes at Goodwood, signalling that Circus Maximus, Wichita and Vatican City could contest the monster clash with Siskin, Mohaather and Kameko on Wednesday.

The Ballydoyle trainer admitted he doesn't know how high Queen Anne hero Circus Maximus could fly virtue of his battling racing style, adding that Wichita is improving with each month and Vatican City will relish returning to a mile.

"We think they're all very high class and that this race would suit them well," said O'Brien.

"We were very happy with Circus Maximus. He never wins by far and is the same in his work, he’d just about put his head in front or wait for another horse no matter what you work him with, so we don't know what his limit is."

Circus Maximus: just edged out by Too Darn Hot in last year's Qatar Sussex StakesCredit: Edward Whitaker

He added of Wichita, who finished closest to Kameko in the 2,000 Guineas before finishing third to Palace Pier and Pinatubo at Royal Ascot: "We were delighted with his run in the St James's Palace Stakes and he's coming forward all the time – we think he's really maturing.

"He's a massive horse and we think every month that goes by he's progressing."

The mile contest will see a rematch of the Irish 2,000 Guineas 1-2 as Siskin locks horns with Vatican City, and O'Brien is looking forward to seeing the brother of Gleneagles in a differently run race at the West Sussex venue.

"Originally the plan with Vatican City was to go straight to Goodwood after the Irish 2,000 Guineas, but we decided to let him take his chance in the Derby, when he didn’t get the trip," he said.

"It was a funny race at the Curragh. We had the pace in it and it was probably slow enough for any of our horses. It just became a bit of a mess and everything was in it at the three-furlong pole, it was just who was going to get the run after that.

"They ended up sprinting by the line and when you see horses being hard to pull up at the Curragh and running up towards the boards [after the line], it's usually not a good sign and usually means it wasn't a truly run race."

He added: "It was a little bit of a non-event for Vatican City and he went by the line very well, but it was his first run of the season and he had two soft runs last year.

"He will have learned a lot from Epsom and he still ran very respectably but we think going back to a mile will suit much better."

Vatican City (pink silks, right): came home well to claim second behind Siskin in the Tattersalls Irish 2,000 GuineasCredit: Patrick McCann (racingpost.com/photos)

Last year's Coventry Stakes scorer Arizona also holds an entry for the Sussex Stakes, but is an uncertain runner.

"We haven't done a good job with him this year, it's all been a bit of a mess," said O'Brien.

"He's working very well and is very happy in himself at the moment, we just have to pick the right spot for him. His three runs this season have been a bit of a disaster for him tactically.

"We feel we haven't got him right. I'd say at the moment he's more likely not to run than to run, but all those things could change."

He added: "His last two pieces of work have been very good and we've just changed a few things with him. We think he's not far away from getting back to where he should be."

Aidan O'Brien on Arizona: 'His last two pieces of work have been very good and we've just changed a few things with him'Credit: Edward Whitaker

Lancaster House is the only other Ballydoyle entry in the Wednesday highlight, but a tilt at the Lennox Stakes on Tuesday is preferred at this stage, having chased home Romanised in the Minstrel Stakes at the Curragh last weekend.

A success in the Group 2 on the first day could set the Tipperary team up nicely for the Goodwood Cup, with Irish Derby winner Santiago on course for a duel with star stayer Stradivarius.

The three-year-old, who will receive 15lb from last month's runaway Gold Cup hero at Ascot, is a general 11-4 to extend his winning sequence at the expense of John Gosden's colossus.

O'Brien indicated Santiago will probably tackle the St Leger after Goodwood and that Derby winner Serpentine is unlikely to join him at Doncaster. He is instead set to run in the Grand Prix de Paris with a view to potentially taking in the Prix de l'Arc de Triomphe.

Epsom sixth Mogul could be part of O'Brien's Goodwood team, with the Group 3 Gordon Stakes on Thursday under consideration.

O'Brien said: "He seems to have come out of the Derby well. He's a big, strong, powerful horse who's made like a miler and he's not the easiest to get fit, even though he's very clear-winded. He carries weight and we're just trying to get it off him.

Mogul: on track to run in the Group 3 John Pearce Racing Gordon Stakes on ThursdayCredit: Patrick McCann

"We think this race will suit him well. We're not really sure how far he'll stay. We think he'll get a mile and a half but it wouldn't be a surprise if we had to go back in trip."

Other notable runners that O'Brien could saddle next week at Goodwood include Chesham Stakes scorer Battleground, who has the option of the Group 2 Vintage Stakes on Tuesday, and Magic Wand, a best-priced 5-1 chance for the Group 1 Nassau Stakes on Thursday.

O'Brien will not attend Goodwood as Ireland's 14-day quarantine period still applies to those returning from Britain.

He is understood to be using the best British riders available for his second- and third-string mounts over the course of the week.

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