Promising colt Spieth has passed his first test down the Flemington straight, but trainer Bryce Heys and jockey Craig Williams are confident there is improvement to come.

Sydney-based Heys was keen to try Spieth down the straight for the first time in Saturday's Goulburn Murray Handicap (1100m) against his own age, and the up-and-coming sprinter drew clear to defeat Lord Von Costa by three-quarters of a length with the same margin to Rich Charm third.

It gave Heys, who started training about 18 months ago, his first Flemington winner.

But despite the victory, Heys said things didn't pan out how he had hoped early in the race when Spieth, the $2.80 favourite, was unable to get cover in the first part of the event.

And he insists the colt will be able to unleash a more effective sprint on drier ground than the soft conditions he raced on.

"He had to overcome things today," Heys said.

"With all due respect to the quality of the opposition, it's probably going to get harder for him from here. It got sticky there through the early stages but he got the job done."

Craig Williams was able to find cover by mid-race on Spieth and then the colt sprinted through to hit the front approaching the 100m to land his third-straight win after victories at Kembla Grange and Rosehill.

"I think running on a soft track today just nullified that real burst of speed that he does have," Heys said.

Heys will see how Spieth comes through Saturday's race but is keen to run him again in the Listed Creswick Series Final (1200m) at Flemington in two weeks.

Craig Williams rode Spieth in his first three starts last spring, including his seventh in the Caulfield Guineas Prelude, and believes Saturday's experience will help him heading to the Creswick Series Final.

"He showed signs that he's going to keep improving on his performance today and the way he felt on and off the bridle throughout the race," Williams said.

"Most importantly when it counted late he was quite solid and strong.

"He a nice horse and potentially feels like a horse that could be figuring in some nice sprint races over the spring carnival."