The usually understated O'Brien stated he might be the best horse he ever trained -- quite some claim given the champions like Galileo and Giants Causeway he has handled.
"He's incredible - a different creature to what we've ever seen before,"O'Brien said after he won his first race by twelve lengths in Ireland.
However So You Think has not lived up to the hype since.
He has not run on dirt but the experts say he has a decent chance on Saturday and the odds-makers agree, having pegged him at 5/1.
O'Brien thinks Saturday's race might prove his point --and he is trying an extra trick to get So You Think focused properly.
"I'm very happy with the horse," O'Brien said. "He's a very relaxed horse in his races and sometimes can become too relaxed so we put a pair of blinkers on him just to try and make him concentrate a little bit more."
"We think we are going to be positive because he travels so well in a race and then he keeps rolling.
"From his gate position, we will be positive with him.
"It looked like he had a tough race at Ascot, but when we got him on the scales at home we found he hadn't lost a kilo. I couldn't believe it.
"The boys (Coolmore) have said he might race on next year and obviously if he does I would be very pleased.
"If he hits the gate, we won't be holding him back.
"We think he's a great traveler through his races, he's tactically sharp and he's a very mature, seasoned horse.
"We've always thought the world of this horse, he was a very good horse before he joined us and what makes him unique is his high cruising speed.
"Horses like that, the better the race, the better they are. We think he has the attributes you need for the Classic - a good cruising speed, he's tactically quick, he's brave but we don't know about the dirt because he hasn't run on it before."
Uncle Mo is the 5-2 odds favorite in the 1 1/4-mile Classic, the top event in American racing which goes off at 7pm New York time on Saturday night.
Second favorite is the filly Havre de Grace at 3-1 and then So You Think' followed by Flat Out at 6-1 in the field of 12 in the feature.
Here's a promotional video for the Breeder's Cup 2011: