"When you look at the Guineas at Riccarton, it tends to be run hard," says O'Sullivan.
"They roll around the big bend at good speed and I think any horse who might struggle at the 1600m can be found out.
"I am not saying that will be the favourite because we don't know that but I know it won't be our horse.
"He is bred and was bought to win 2400m races eventually so we have no worries at the trip."
O'Sullivan says because of his busy schedule to get ready for the classic, Rocket Spade may have been below his best when fourth to Need I Say More in the Sarten Memorial at Te Rapa last start, but he believes he is bang-on for the Guineas.
Another trainer who thinks he has a genuine 1600m horse is Andrew Forsman, who co-trains Aegon with Murray Baker.
The slight gelding won the Hawke's Bay Guineas with an explosive finish beating among others Need I Say More, who had no luck from a wide draw.
Forsman says while Aegon has had only two starts and is immature, he seems to be getting away with it.
"He still has some maturing to do but he is very well in himself," he says.
"We expect to be off the speed and hitting the line hard and I am not worried about the 1600m or the track.
"Need I Say More is a very fast horse who is going to be hard to beat, so a lot might depend on the tempo of the race.
"But we couldn't be happier with our horse."