Ivan Cleary has questioned why Brisbane prop Tom Flegler wasn't sent off for a high shot that knocked out Penrith captain Isaah Yeo, as Penrith scraped home 18-12 over the Broncos.

In far from their best night of the year, the Panthers missed a season-high 66 tackles as they saw an 18-0 lead almost evaporate in an almighty late scare.

But Cleary was filthy over referee Ben Cummins' decision not to march Flegler in the ninth minute, instead only sin-binning him as Yeo was immediately ruled out of the game.

A frustrated Cleary claimed after the match that the benchmarks had changed since the start of the NRL's crackdown, dating back to Magic Round two months ago.

"He's knocked out as soon as he hit him. It's an illegal act. That's why he got sent to the bin," Cleary said.

"So I don't know what you've got to do to get sent off.

"If it was Magic Round he would have been sent off.

"Nothing against Flegler, but he hit him high and flush and knocked him out.

"What more do you need? It certainly affected us a lot worse than it did them."

Yeo has a history of concussions, but Cleary said after the game the Panthers lock was doing alright.

The same couldn't be said of the club's defence after they recovered from a tryless first half to lead 18-0 after 56 minutes.

The 66 tackles they missed was the most of any team this year, and was well more than double their average of 27 for the season.

Brisbane forwards Kobe Hetherington and Ethan Bullemor both crashed through their middle late in uncharacteristic scenes, threatening a grandstand finish before Penrith held on.

"It's far too many (misses)," Cleary said.

"It hasn't been there all year. But it's been a bit lately.

"The missed tackle can actually be a little bit out of context sometimes. I thought that was probably the case in the first half.

"In the second half it wasn't out of context, we were missing tackles that we should have made."

Regardless, the win was still enough to keep the Panthers level on points with Melbourne at the top of the ladder ahead of their blockbuster clash.

Much like the Panthers, the Storm had their own struggles in edging North Queensland on Friday night.

Nathan Cleary won't return for that game, meaning the Panthers' attack must also step up before then.

Their only first-half points came via a penalty goal and 42-metre two-point field goal from Dylan Edwards on the siren.

Viliame Kikau was menacing on the left edge throughout, setting up their first try when he put Brian To'o over after Tyrone May and Jarome Luai linked in the lead up.

Stephen Crichton also impressed on the right, setting up one try with a no-look flick for Charlie Staines and scoring the Panthers' other himself.

"You're never happy with a loss but from where we were last week to now against Penrith ... we've made some big strides," Broncos coach Kevin Walters said.