The Penrith Panthers during their loss to the Bulldogs.

Penrith coach Ivan Cleary lamented his side's lack of polish in the first half as an invitation for Canterbury to pounce after their 16-8 loss at Bankwest Stadium on Saturday night.

The Panthers led 8-6 at half-time but two errors in their possession while the Bulldogs were down to 12 men with Aiden Tolman in the sin bin proved disastrous.

With key playmakers Nathan Cleary and James Maloney struggling to make an impact the Panthers were held scoreless in the second half by a swarming and desperate Bulldogs defence.

"I thought we lacked a bit of polish and under pressure we weren't able to execute," Ivan Cleary said.

"I wasn't happy with the first half. We let them out of their end and couldn't build enough pressure.

"I thought we invited them into a scrap and they were good enough to win the scrap. I guess we were just behind the eight-ball for the rest of the game. They scrambled well and did enough to stop us."

Cleary wouldn't weigh in on a try to Jack Cogger in the second half that enabled the Bulldogs to take an eight-point advantage off a scrum play.

The NRL Bunker ruled in favour of the Bulldogs playmaker despite replays indicating he may have lost possession reaching out for the line.

"It was obviously a close one, I didn't look at it closely," Cleary said.

"I think deep down we knew it was going to be a tough game so complacency certainly wasn't an issue.

"I thought our preparation was the best it has been for some time. We're not in a position to be complacent. I thought they spoiled really well.

"We didn't play well and that's disappointing."

The Panthers weren't helped by the fact utility Jarome Luai played just six minutes after copping an accidental poke to the eye from Dylan Napa.

Luai's eye was covered up by swelling following the match with scans to confirm if there is any further damage.

"He was straight off, he couldn't see," Cleary said.

"It's closed up and it's pretty black but I'm not too sure at this stage."