Chris Waller counts himself lucky to have seen US Triple Crown winner American Pharaoh in the flesh and he was thrilled to provide the stallion with his first Australian victory.

Trained by legendary horseman Bob Baffert, American Pharaoh was a star on the track and has made an immediate impact with his northern hemisphere progeny.

The Waller-trained Head Of State became the sire's first southern-hemisphere winner at Warwick Farm on Wednesday from just a handful of horses to race.

Head Of State fetched $850,000 as a yearling and is owed by a partnership which includes Coolmore, who orchestrated the original meeting between Waller and Baffert.

"I was lucky enough to meet the horse and the trainer, Bob Baffert, in America and it was at Coolmore," Waller said.

"It was one of my proudest moments to get over there for the Kentucky Derby and to be training one by him, it's good."

Head Of State is not among nominations for the Golden Slipper as Waller believes the longer distances of the Sires' Produce and Champagne Stakes will be more to his liking.

"You can see he is still a little bit green. He just wobbled around the bend a little bit," Waller said.

"He's probably not a natural on-pace horse but he did everything right to let down strongly and he will take a lot of improvement from it.

"I would think he is a Sires', Champagne type of horse but if not, he will be a Guineas horse in the spring."

Jockey James McDonald was equally enthusiastic, describing Head Of State as a "beauty".

"It's really nice to get a good, dominant win on the board because I reckon he's a pretty good horse who will measure up in good races come 1400, a mile," McDonald said.

"He's just got a lovely action and a good mindset."

McDonald went on to land a treble at the midweek meeting, adding wins aboard the Waller-trained Seleque and Newsreader for John O'Shea.