Saxon Warrior is in line to renew rivalry with Roaring Lion in the Juddmonte International at York next week.
The 2,000 Guineas winner will lead the charge on the Knavesmire, having finished just a neck behind Roaring Lion in the Coral Eclipse at Sandown last month.
It will be the fifth meeting between the two horses, having finished twice ahead of each other.
Saxon Warrior had experienced just a seven-day turnaround, after he was runner-up in the Irish Derby, and has been afforded a long break since.
"We gave hime a little rest after Sandown, he's in good form and that will be his first start back again," O'Brien said. "Donnacha [O'Brien] rode him this morning and seems to be very happy with him.
"I think Joseph [O'Brien] is thinking of running Latrobe, it will be a tough, competitive race and it will be lovely for our horse to start off there and hopefully he'll run well."
The Galileo colt has had a fine season, having won the Queen’s Vase at Royal Ascot and the Grand Prix de Paris at Longchamp.
Kew Gardens is now a leading contender for the St Leger at Doncaster, but will first head to York for the Group Two over a mile and a half.
O’Brien said: “He (Kew Gardens) is probably going to go to the Voltigeur for a trial and go from there.”
Charlie Appleby hopes Old Persian can also enhance his Leger credentials in the Great Voltigeur.
A winner of the King Edward VII Stakes at Royal Ascot in June, who is as short as 14-1 for the final Classic of the season, will bid to get his career back on track after failing to feature in the Irish Derby.
The Newmarket handler said: “Old Persian is heading to the Great Voltigeur.
“Whereas he sat handy at Ascot, the gallop was different in the Irish Derby and it didn’t work out.
“He has had a nice break since then as we backed him up quick enough in Ireland after Ascot.”
O'Brien also added that Forever Together, the Oaks winner and Irish Oaks runner-up, will be joined in the Yorkshire Oaks line-up by Magic Wand, the Ribblesdale Stakes winner who scoped dirty after running fifth in the Irish Oaks,and Bye Bye Baby, who was fourth at the Curragh.