Tournament directors state teams must bowl their 20 overs within 90 minutes with the Heat taking 96 minutes.

McCullum had previously received a warning for the same offence.

But the Heat are expected to contest the suspension after several delays were caused by third umpire referrals and a concussion check to Perth’s Sam White.

Australian coach Darren Lehmann was dumfounded at the possible one-match sanction.

“It’s ridiculous. If you don’t mind me, Howie. We want McCullum playing,” Lehmann said during Chanell Ten’s broadcast.

“Speed it up, fine them all, if it’s that bad, but we want them playing cricket.”

Mark Waugh was in agreeance.

“Exactly, take it out of his pay packet if it’s that bad,” he said.

The Heat were fined for the same offence against Hobart at the Gabba on December 30 after taking 95 minutes to complete their overs with a second sanction bringing with it a mandatory one-match suspension to the captain.  

McCullum’s loss would compound the absence of Australian ODI call-up Chris Lynn ahead of the Heat’s clash with the Melbourne Stars on January 17.