The Ballydoyle trainer's possible Spring Carnival team could have two more members after stablemates Tower Of London and Grosvener Square fought out a thrilling Curragh Cup in Ireland.
The master horseman nominated the 2024 Lexus Melbourne Cup as a possible target for the duo, who are both sons of Galileo.
Grosvenor Square took off with a huge lead in the 2816-metre Group 2 event, which was run in the early hours of Sunday, Australian time, and looked home with 400m to run only to be reeled in late by Tower Of London, who launched a powerful finish under Ryan Moore.
Vauban, last year's Melbourne Cup beaten favourite, was seven lengths away third.
Tower Of London and Grosvenor Square have races to target in Europe before any possible trip to Australia, but both have what it takes to be competitive at Flemington in November according to O'Brien.
"He could come back here for the (Irish St) Leger," O'Brien said of Tower Of London.
"He's a great horse to have and can travel anywhere. He loves travelling, he could be a Melbourne Cup horse – he could be anything." - Aidan O'Brien
"Grosvenor Square ran a great race and he's a trip horse. He wanted to go the distance and could be a Melbourne Cup horse.
"He's a good economical galloper with a good staying pedigree."
The Curragh Cup success was the sixth win for Tower Of London, a Northern Hemisphere four-year-old, who won the Group 2 Dubai Gold Cup over 3200m at Meydan in May.
Grosvenor Square is a lightly-raced three-year-old who won the Group 3 Eyrefield Stakes (1810m) last October and the Curragh Cup was his first start since finishing seventh in the Group 1 Irish Derby (2414m).
