"He hit the lead and then only battled and allowed the other horse to come back and beat him and I knew then he wasn't spot on.
"I think he had been suffering from allergies with the change of season so we gave him a break and he has come back better.
"His work has been really good and he feels back to his old self."
So would that make him a good thing with only five rivals in the 2200m mobile last race on the card?
"I'd like to think so but it may not be that easy," explains Purdon. "A horse like Kango likes to lead and run hard and if he did that my horse isn't ready to attack him fresh up.
"So we might be a little bit calmer early and if the tempo suits and/or he ends up in the one-one he will get his chance to win but if he is back and they run home very fast it could be tricky."
That is the usual early campaign warning from Purdon when his best horses return and they, like most good horses, are usually most vulnerable in that state.
The small field should help and anything like a 100 per cent Self Assured should be able to sit parked outside Kango and still win.
So then it becomes a question of price and punters would want to be getting at least $1.80 to take the risk and $2 to make it worthwhile.
Kango has the fitness to control the race while B D Joe is another who is suited by the conditions but all three will probably strip fitter for a $20,000 Cambridge Classic next Thursday.
"Our horse will definitely be better for next week and then the Free-For-All on February 12 when he takes on South Coast Arden," says Purdon.
Safely through those, Self Assured and the other big names have a tasty autumn menu of The Race for $900,000 at Cambridge on April 14 and the $400,000 Auckland Cup on May 29 with some other healthy targets in between.
Purdon was to have started superstar three-year-old Akuta at Alexandra Park tonight but the only race he ended up being eligible for was alongside Self Assured.
So he will wait for Cambridge next week as he prepares for Alexandra Park's new Harness Million meeting on February 12.
The Purdon/Cullen stable does, however, have fellow three-year-olds Franco Mac and Cyrus in the opener tonight, with Franco Mac having improved so much he should make it four wins on end.
Sires' Stakes winner Franco Indie also resumes but at Addington where he should win race five even against older horses as have none of his rivals have his raw class.
"He has been working really well and there won't be much between Akuta and him for the Harness Million," says Purdon.