There was little in it as Mach Dan and Zeuss Bromac emerged from the fray to stamp themselves as TAB Breeders Crown contenders in eventful IRT Australia three-year-old colts and geldings semi-finals.

Mach Dan came late to pip Jilliby Nitro at the post and Zeuss Bromac won a brusing battle to the line with top tier types Pacifico Dream and Willie Go West to reaffirm that this remains an extremely competitive class.

We begin with the first semi-final, and it was Emma Stewart's Mach Three gelding, Mach Dan, who further proved his Group 1 chops for reinsman Greg Sugars.

"He's in a real purple patch at the minute," Sugars told Trots Vision. "The trip away (to New South Wales) helped him step up his game and he's come back in terrific order."

And he needed to be good in the running, with the race dramatically changing complexion leading into the final turn.

Leader Imnopumpkin hung out which disturbed the running line, forcing favourite Loorrim Lake to temporarily veer three-wide and then sit outside Ranger Bomb, who had snuck up on the inside.

Rounding the bend Loorrim Lake then appeared to hang in and the lead pair were soon swamped, first by Jilliby Nitro and then by Mach Dan.

"We went from getting a good run through to shuffling up quite quickly, but thankfully it all worked out fine for me," Sugars said.

"It's good to see him (win in) two completely different ways. In the heat he obviously dominated from in front and held them off quite comfortably, tonight he's come from last and rounded them up.

"It gives you hope going forward that, however the cards fall in the draw, he's going to be a chance."

Joining the first pair in advancing to next week's semi-finals were third-placed Perfect Stride, Mirragon (fourth), Scorcha and Loorrim Lake.

They will be joined by Zeuss Bromac, Pacifico Dream, Willie Go West, Monsieur Delacour, Jemsoms Pet and Sahara Sirocco after they finished in that order in the second semi-final.

After an initial disruption, when Big Black Diamond galloped on the pegs and then Krafty Bart followed suit, the second semi-final was a more settled affair once Chris Alford advanced favourite Willie Go West to the lead from gate seven and Kerryn Manning hustled Zuess Bromac into the breeze from the second row.

"He got a good run through early," Manning told Trots Vision. "A little bit of a scrimmage on the first turn messed up a few others plans and I was able to lob the death without really doing a lot."

Decision time then came with a lap to go when Kate Gath advanced on highly-fanced Pacifico Dream, with Manning initially hesitant to allow the Stewart runner to glide into the breeze.

"I was happy to sit there and when Kate came I was in two minds whether to hand up.

"I had a little look at (leader) Chris (Alford) and he said no, Kate kept coming and it's not a bad horse to sit on.

"I was in a good spot most of the way, maybe he had to come out a little early - I was umming and aarghing whether to stay on Kate's back and chance my arm or come out. So he had to come out fairly early in the back straight and do a fair bit of work in the last lap."

But he proved up to it, clawing over the leaders amid a 27.5-second last quarter to record an eye-catching win and potentially set himself up with favourtism for the final.

"He seems a nice little horse," Manning said. "He's not very big at all, he's quite nuggety, a cute little fella and it was a pleasure to get to drive him. It was a really good run, he kept going to the line and the run will probably do him good."

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