"He was fine the next morning and went out into the paddock tired but with no real problems," Purdon told the Herald.
"But when I brought him back in about an hour and a half later because of the heat, he was quite sore in the hooves.
"And that didn't improve when we put him back in his box or today (Sunday) like we hoped it would and he is still sore now.
"We have had the vet to him and we are pretty sure it is in his hooves and probably a concussion thing from the race.
"But we won't know exactly how bad it is and whether that is all that is wrong until we have a few more days with him.
"So it has come as a bit of a shock but at this stage the vet thinks it is related to a hard run on the hard track."
Purdon did not think the brutally hard run Lazarus had on Friday night was the reason for his problems.
"I think even if he had an easier run and won he would have been sore afterwards. I just think the track has got to his hooves." The five-year-old, who was sensational winning the Inter Dominion in Perth last month, will be swum this week to try and maintain his fitness while he is kept off the track.
"But the WA Cup this week is definitely gone for him and the next target will be the Hunter Cup.
"We definitely haven't give up getting him to that and we have nearly three weeks but it is also not certain he will make it.
"It is all a bit up in the air at the moment."
The two-time New Zealand Cup winner was the hot favourite for not only the WA and Hunter Cups, the latter at Melton on February 3, but the A$750,000 Miracle Mile at Menangle on February 24.
"I hope by Miracle Mile time he will be fine, unless there was something else wrong with him, but obviously we can't guarantee that."
If Lazarus does miss the A$500,000 Hunter Cup the Purdon-Rasmussen stable will still have Heaven Rocks in the race, with the latter set to make his Australian debut in the Ballarat Cup this Saturday.
But the stable will resist any temptation to step Auckland Cup winner Vincent up to the Hunter Cup as Lazarus's replacement.
"Vincent has the Chariots Of Fire at Menangle the week after so I don't think we would target the Hunter with him but at this stage we are still hoping to have Laz there."
Stablemate Ultimate Machete also pulled up slightly sore after his fourth in the Fremantle Cup but nowhere as bad as Lazarus.
"He was like that for a few days after he won the Golden Nugget here last month too but I still very much expect him to make it to the Chariots Of Fire on Feb 10 and race on this campaign."