"I was happy with him three starts ago when he ran second and then again in the Auckland Cup when he ran on well for sixth after being checked at the 400m.
"But last start was a total mystery. His work has been really good since so it is just one of those runs you are better off turning the page on."
If punters can do that then they must give Mach Shard a chance in the main pace on Friday because at his best he is up to winning this, with the obvious dangers on Triple Eight and Matt Damon.
As is so often the case in small field sprint races at Alexandra Park the start and early tactics will be crucial because if one of the favourites gets the lead horses like Mach Shard and Triple Eight are not known as attackers so it may be a case of who dares wins.
Matt Damon's draw may give him the best hope of heading forward and controlling the race and he has been excellent in both his northern starts so may be the horse to beat.
Purdon and training partner Scott Phelan have a strong hand throughout the programme including a representative in both juvenile races as the two-year-olds make a later than usual start to the season.
They have expensive sales purchase Major Perry (R7, No6) in the boy's juvenile and homebred filly Artisan (R9, No3) in the girls race and both look chances on trials form.
"We like them both and while it is hard to tell with early season juveniles because you don't know the opposition that well they should both be close up."
Purdon suggests Raven Banner (R4, No7) will be one of the stable's hardest to beat after some brave performances in better fields at the Cup carnival that ended 2020 at Alexandra Park while Bettor Listen (R2, No11) will win a maiden one day but faces a second line draw.
The meeting presents some interesting puzzles for punters, with many of the true Alexandra Park horses having not raced for three weeks, the unknown elements of the debutante juveniles and a couple of 2200m standing start handicap trot.