Bulldogs prop David Klemmer.

Canterbury skipper Josh Jackson has defended the actions of David Klemmer after the Bulldogs prop was sin-binned late in the 22-14 loss to the Panthers on Friday night.

In an explosive final 10 minutes, several scuffles broke out and things boiled over after a massive hit from Panthers centre Dean Whare on Jeremy Marshall-King.

Klemmer and Panthers prop Trent Merrin had sparked a push and shove at a scrum just minutes before the Whare tackle and both big men were clearly not prepared to back down.

With the bad blood simmering, it was Klemmer who was sent for an early shower as he intervened following the shot on Marshall-King.

"I didn't see much until the replay but [Merrin's] thrown a slap or punch and hit Klem in the side of the face [at that scrum]. I've seen plenty of them pulled back and a player get sent for 10 but it was play on," Jackson said.

"Later on in the game Dave shoves a bloke for making what he thought was an illegal tackle and gets sent for that. I think the case of Klem it was just him sticking up for one of his players."

The sin-binning capped a frustrating evening for the Bulldogs, who were outplayed in the second half after taking a 12-8 lead into the break.

Canterbury started the game well, racing out to a 12-2 lead, but a try just before half-time to Corey Harawira-Naera sparked Penrith into action.

"That's what it was the whole game, exactly that," Jackson said.

"They out-enthused us and when we did have a little bit of possession in the second half we made crucial errors.

"You can't win a game of footy like that."

Bulldogs coach Dean Pay expressed his disappointment and admitted his side must work on their  structures if they are to turn around a 2-6 start to the season.

"It was really frustrating," Pay said. "It's like every week, we missed out on a couple of opportunities. For one reason or another we can't crack those opportunities or take them at a given moment.

"It is an issue. Our first half was OK. The errors in the second half is what killed us. And we couldn't handle their line speed. That's what it came down to.

"We've got to learn to make sure our line speed is as aggressive as theirs is."