"But he had a good break over summer and this time in he has definitely thickened and strengthened up.
"He looks tremendous - he is the complete package."
Pierro had not started in a barrier trial for 12 months but his competitive streak took over when he was taken out onto the course by trackwork rider Mark Newnham.
"As soon as Pierro was saddled up and got out there, he pumped himself up as the good ones tend to do," Kolivos said. "He knew he was there to do something."
Despite Pierro's impressive trial, Waterhouse and Kolivos have not decided on a comeback race yet.
"There are a few options being tossed around but nothing will be set in stone for another week or so as Gai just wants to see how he pulls up after the trial.
"He has been nominated for the Newmarket Handicap at Flemington just in case we are possibly tempted to run him there. But equally he might stay in Sydney and see what emerges over the next few weeks.
"His main goals are towards the end of the autumn in the weight-for-age races and maybe the Doncaster. We will be guided by Gai as she is with the horse every day."
Pierro, winner of the Golden Slipper last year, was a surprise entry for The BMW, run at Rosehill on April 6.
The Australian Turf Club took 63 nominations for The BMW including early Melbourne Cup favourite Puissance De Lune, Fiorente, Gatewood, Glencadam Gold, Kelinni, Mawingo, Fiveandahalfstar, Le Roi, Laser Hawk, Maluckyday and Niwot.
In other Sydney news, Happy Galaxy steps out in the group two Expressway Stakes (1200m) at Warwick Farm on Saturday.
Happy Galaxy has won three of his four starts this campaign, including his first black-type test in the Zeditave Stakes at Caulfield last month.
He is due to return from Melbourne to Team Hawkes' Sydney base on Friday morning, ahead of his toughest test to date.
"Obviously, he's taking on group two, weight-for-age level," co-trainer Michael Hawkes said, "but in saying that, he's only a 3-year-old and he gets in well at the weights. And he's the fittest horse in the race.
"It's a class field, obviously. These fields, you can't take them too lightly.
"But he's drawn a good gate, barrier two, he's an on-speed runner and he'll put himself right there. It's just a matter of whether he's good enough on the day."
The Expressway has attracted several big names including perennial runners Danleigh and Centennial Park who will both line up in the race for the fourth consecutive year.
