Latrobe leaves from Europe on Thursday (Friday AEDT) and will arrive with the final eight international spring carnival contenders on Saturday.
Williams is still unsure if there is a spot in the quarantine centre at Werribee for Latrobe's travelling companion Master Of Reality.
"We don't know yet. Probably we'll know later in the day but Latrobe could be paired with another horse at Werribee," Williams said.
"Joseph thinks the horse has really thrived so he's keen to bring him.
"But we are also very wary about taking his mate away from him, so we need to get his mate on the plane with him."
Williams and his father Lloyd won last year's Melbourne Cup with the O'Brien-trained Rekindling and believes Latrobe has the potential to be better than Rekindling.
"Rekindling was the perfect horse to travel as it turned out," Williams said.
"He took everything in his stride, didn't take a lot of work and was a natural stayer.
"This horse is going to be a very good four-year-old.
"Mentally he's probably not quite as ready as Rekindling but having said that Joseph thinks that he's really come on.
"I think you'll see the best of him over a mile-and-a-half whereas Rekindling is just a dead-set two-mile horse."
Brenton Avdulla has been booked to ride Latrobe in the Melbourne Cup in which he has 52kg.
Latrobe is a $17 chance in latest Melbourne Cup betting with Avilius the $9 favourite.