Cullen's comments come after star-import Leon Rosborough left the court in the second quarter after rolling his ankle after taking a rebound.

The Vanguard University alumni failed to take part in the rest of the game and his immediate playing future is still up in the air this morning, as he seeks medical advice and likely intensive physiotherapy ahead of his side's sudden-death semi-final this weekend.

Cullen admitted he had made a mistake by playing Rosborough and hoped the prognosis was not as bad as initially feared.

"In hindsight it's close to being the biggest coaching blunder of all time because I shouldn't have played him. I should have rested everyone for a game that doesn't matter," Cullen said.

"Now I have an injury like that, I'd call that a coaching stuff-up.

"We really just wanted to have a good game, and even myself got carried away with that fact that we wanted to have a good show (for the crowd)."

After performing poorly the week before to score only 50 points and lose to Moss Vale, Illawarra pulled out one of their best performances of the season to light up the scoreboard early on.

The Demons drew level in the shadows of half-time and looked capable of going on with the job, but Rosborough's injury took the wind out of the home side's sails with the Hawks enjoying a comfortable eight-point lead at the long break.

"At third quarter we started making a bit of a charge but then we got with with a foul count 6-1, we just couldn't get a flow on, but it was probably in the back of our mind's that it was a dead-rubber," Cullen said.

"Nothing went for us with Leon getting hurt, and with Frenchie (Steve McCanna) not playing (through injury).

"Really it was probably one cases where we still needed to play and get rhythm and for nothing going our way we played aldl right.

"We tried everything but I shouldn't have because the game meant squat (nothing)."

The Demons could be dealt a double blow ahead of their semi-final, in a yet to be determined location, with McCanna to face a tribunal this week to hear his case after getting involved in a shoving match with a Wagga Heat player two weeks ago.