Queensland coach Billy Slater refused to criticise the officiating of Ashley Klein after he sin-binned Maroons backrower Felise Kaufusi at a critical stage in State of Origin II on Sunday.

Klein's opening game performance had been criticised by NSW coach Brad Fittler, who accused the referee of allowing Queensland to stray offside and slow down the ruck.

But Klein showed he was willing to send infringing players to the sin bin when Kaufusi was dismissed for a 10-minute spell late in the first half.

The Blues then scored just before half-time for a 14-12 lead at the break.

While the Maroons battled when reduced to 12 men, the Blues' period of numerical advantage began to tell late on with NSW scoring 30 unanswered second-half points to win 44-12 and square the series.

"Fatigue plays a part in the game and when you're down to 12 men you are a lot more fatigued," Slater said.

"I'll have to go back and look at the penalties individually but that's the referees' job. We won't use that as an excuse."

Klein had penalised the Maroons for a quartet of infringements late in the first half when NSW were camped on Queensland's line.

Skipper Daly Cherry-Evans twice handed NSW fresh sets of six, while hooker Harry Grant gifted one to the Blues with an attempt to slow down the ruck.

It was the fourth of the infringements which prompted Klein to lay down the law when Kaufusi was part of a tackle to halt NSW prop Junior Paulo on the line.

Kaufusi lay over Paulo for the best part of 10 seconds, prompting Klein to send the Maroons back-rower for a 10-minute spell.

Former NSW coach Phil Gould took issue with Klein's decision in commentary for the Nine Network, claiming the Maroons deserved a team warning before being reduced to 12.

Cherry-Evans said the Maroons were surprised.

"I felt the decision was made quickly considering the amount of infringements we had," the Queensland skipper said.

"You don't know when you are going to get those decisions against you.

"Every time you get someone sent for 10 it does come as a bit of a shock."