Sydney Roosters’ rookie halves were taught a heavy lesson in Monday’s NRL trouncing to Penrith, says coach Trent Robinson.

With star halfback Mitchell Pearce ruled out pre-game with a calf injury, Robinson opted to call up youngster Ryan Matterson to partner fellow greenhorn Connor Watson against the Panthers.

And the results were disastrous, with Robinson bemoaning the loss of his chief playmaker.

“Definitely when you lose your halfback and the guy that guides you around the park, it’s very difficult. But that doesn’t miss tackles either,” Robinson said.

“(Because of) the pressure that we couldn’t apply to them, they end up having a fair bit of freedom in play. So if we can’t put them into awkward positions through good kicks and pressure, then they play with more freedom.”

Robinson, whose side have now lost seven of their past eight games to remain second last, blamed his team’s poor defensive effort purely on their last-tackle options.

It was the fifth time this season Robinson’s men have lost by at least 20 points.

“Their whole 80 minutes was front-foot attack. So the ball was in good positions for them for the whole game, and that’s confidence for them. It ended up in missed tackles and tries eventually,” he said.

Robinson admitted Matterson and Watson, who boast 21 games experience between them, were taught a harsh lesson.

“It’s hard when you take an experienced player out and you ask those guys to do their job,” he said.

“That’s NRL. We’ve faced it a lot this year. It’s really tough.”

Ironically, Robinson was full of praise for Penrith’s teenage halfback in Nathan Cleary.

“He was exceptional. He led from the front as an 18-year-old. It’s pretty impressive,” he said.

Pearce is expected to return for next week’s daunting clash against North Queensland.