Brad Fittler has slammed the ongoing criticism of NSW Blues and Penrith Panthers' halfback Nathan Cleary after Game 1 of the State of Origin series, suggesting he didn't let anyone down.

Cleary played arguably his worst Origin game - and possibly the worst game of his short career - during the series-opening defeat to the Maroons in Sydney.

It has left the Blues facing the uphill task of beating the Maroons in both Perth and Brisbane during back-to-back games to have a chance at claiming the series, with a decider at Suncorp often seen as the ultimate test for NSW teams of yesteryear.

Despite Cleary's poor performance - one which has accepted responsibility for - Brad Fittler told The Sydney Morning Herald that the team owed it to him to be better over the rest of the series.

“He is our halfback and our vice-captain,” Fittler told the Sydney Morning Herald.

“The attention that he gets still shocks me. I want to say we let him down on the night – not the other way around.

“We owe it to him to be better. But he has to feel this pain. All the great ones do. And it will only make him better in the next game and beyond that.”

Cleary led the Blues to a 2-0 lead over the Maroons' during last year's series in record-breaking circumstances once total score across two games was combined, before he and Jarome Luai both missed Game 3 with the Queensaldners saving a clean sweep.

Cleary would return late in the season, finish second in the Dally M race and then lead the Panthers to the premiership, beating the South Sydney Rabbitohs in the grand final.

Penrith again sit at the top of the table halfway through the 2022 season, with Cleary a star backing up from Origin as they hammered the Newcastle Knights during Round 14 by 42 points to 6.