Summer plans for The Cleaner are uncertain after the popular galloper ran one of his worst races since becoming a legitimate star of the Australian weight-for-age scene.

For one of the few times in his career The Cleaner let down his legion of fans when he managed to beat just one horse home in the Conquering Stakes at Launceston on Wednesday night.

Having his first start since finishing midfield in the Cox Plate, The Cleaner was sent out an odds-on favourite but was beaten four lengths into seventh place behind Admiral.

Trainer Mick Burles said the lacklustre return had taken him by surprise despite treating The Cleaner for blood viruses since the Melbourne spring carnival.

"I'm a bit baffled, but anyway we'll work it out in the next few days," Burles told Melbourne radio station RSN.

"He's had a lot of blood viruses the last couple of months and he just finished treatment for one last Sunday.

"Whether the antibiotics made him a bit flat, or what has made him a bit flat, I can't answer that."

Burles said The Cleaner would have tests next week before he made a decision on his stable star's immediate future.

"If he's not right I'll chuck him in the paddock," Burles said.

Burles was hoping to use the Tasmanian Stakes at Launceston on December 23 as The Cleaner's lead-up run to next month's $1 million Magic Millions Trophy.