The visitors pulled off a shock on Friday, with a tryscoring double from Herbie Farnworth and an Adam Reynolds field goal helping Brisbane to their first win at BlueBet Stadium since 2009.
Brisbane's defensive resolve deserted them at the back end of last year but aside from a runaway try to Stephen Crichton and a Soni Luke bargeover, they kept the Panthers at bay for long periods.
"It's a really good win for us, Penrith have been a great side for a long time and everyone is chasing them," Walters said.
"It was a tight game and there wasn't much in it and we won't get carried away.
"Defence was one of our things that we wanted to be better at.
"We made some good improvements tonight but as a whole, the effort - particularly on the tryline - that's the best defence I've had since I've been back at the club."
Penrith, for their part, looked clunky.
Without Api Koroisau at hooker and Viliame Kikau in the backrow, the Panthers struggled for attacking outlets and it was only late in the piece that they came alive.
With Brisbane 13-6 up, Luke was able to crash over for a try and he nearly had a second after Nathan Cleary attempted a two-point field goal.
Stand-in Broncos fullback Selwyn Cobbo spilled the ball as he ran it back, with Luke diving on it to score what would have been the matchwinner.
Unfortunately for the diminutive hooker, Jarome Luai was penalised for being offside on the kick chase as Penrith were condemned to a second-straight home defeat.
"I felt we had a lot of opportunities and left a couple of tries out there," said Panthers coach Ivan Cleary.
"We were a little bit disorganised at times, which is pretty standard for round one.
"It was a tough game and a disappointing loss but there's certainly a lot to build on for sure."
It looked like it would be a straightforward night for the Panthers when they surged ahead after just eight minutes.
Canterbury-bound centre Crichton put them ahead after second-rower Liam Martin made an incisive break upfield.
Penrith had the upper hand in territory and possession but Brisbane were able to strike back when Reynolds snuck down a short side and sent Farnworth in at the corner.
Five-eighth Ezra Mam pinballed his way through a hole in the Panthers' line before toeing ahead to set up Farnworth's second.
Martin and Luke Garner both went close for the hosts but Brisbane were able to hold them out.
Cobbo made a couple of errors but Penrith were unable to make use of the territory as their attack struggled to click into gear.
Interchange hooker Luke provided some much-needed spark in the second half and crossed after Reynolds' 71s minute field goal to send the game down to the wire.
But a second try eluded him and allowed Brisbane to hold on for victory.
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