Something has clearly been bothering the superstar talent, with the most likely diagnosis being a kidney problem nobody seems to know how to fix.
To make matters worse, while Have Faith In Me has been racing below par or not at all, Lazarus has emerged as a world-class pacing machine and even Dream About Me has gone past him in the pecking order.
Finally, this week, Have Faith In Me has started to give Purdon reason to take his name literally.
"He has been back in work properly a few weeks and he feels really good," says Purdon.
"The other day I got Tim [Williams, his former driver] to fast work him and when he came off the track he said it was the best he has felt since his three-year-old days.
"So while we haven't been able to fix what we think is a kidney issue, it looks like it has calmed down with the break."
So pleasing as Have Faith In Me's work been, Purdon has booked him on a plane to Melbourne next week where he could resume in the Ballarat Cup on January 21.
"He would need to trial the week before but Ballarat looks the aim and then we can decide what happens."
What happens after that could be paying a late entry fee to the A$500,000 Hunter Cup at Melton on February 4, all going well.
Have Faith In Me's career was so in doubt a few weeks ago he wasn't even nominated for the Hunter, so a A$5000 fee will be paid the Monday before the now mobile 2710m group one to sneak him into the race.
"That will depend on how things go between now and then but I think he could be there," said Purdon.
"I wouldn't think the Victoria Cup [January 28] would be his type of race and I wouldn't want him to race three times in a fortnight so he will miss that."
If Have Faith In Me makes it to Ballarat, and then the Hunter Cup, he will be on a collision course with Inter Dominon-winning stablemate Smolda.
The great old horse heads to A$100,000 South Australia Cup at Globe Derby Park in Adelaide on Saturday night.
Purdon will be travelling across the Tasman to drive him after piloting Lazarus at Cambridge on Friday night.
Lazarus, who hasn't raced since winning the NZ Free-For-All on November 11, has drawn almost ideally at barrier four at Cambridge and with Christen Me drawn the inside of the second line, he will start red hot.
Also well drawn at Cambridge is National Trot winner Quite A Moment in the Flying Stakes, in which age group stars Prince Fearless and Prime Power return.
Meanwhile, Waikiki Beach will make a rare New Zealand appearance when he has a workout at Pukekohe on Saturday before heading to Sydney.
Also on the same workout card and the same flight to Sydney will be unbeaten three-year-old filly Partyon, who is being aimed at the NSW Oaks next month.