The defeat leaves big question marks hanging over their finals credentials and continues their poor run against the Panthers who have now won the past four and nine of the last 12 encounters between the two sides.
The Auckland outfit will fall from fifth to seventh on the premiership ladder and could slip to eighth if the Broncos score a big win over the Titans on Sunday, while the Panthers shook off consecutive defeats to the Roosters and Manly to remain in fourth spot.
"It was a tough one tonight," said Kearney.
"I've got to say I think it came out of nowhere. The lads have had a really good three weeks apart from the result last weekend, and they've trained really well over the course of the week.
"I'm not going to sit here and make excuses. We had moments there, we worked and competed really hard in that first 20-25 minutes and we didn't get a great deal of reward for it.
"But we needed to tough it out and I don't think we did that well enough particularly in the second half."
The Warriors started well but the nightmares of last week's controversial loss to the Sharks came back to haunt them with two forward passes spoiling two early attacking raids.
A run of six straight penalties saw the home side dominate territory and possession throughout the second quarter to score two quick tries with Phillips grounding Luai's grubber before the No7 dived over for their second.
The Warriors went 10 minutes without the football and tiring defence struggled to contain the Panthers free-flowing style but the visitors were fortunate not to concede another try before Luai kicked a penalty to give Penrith a 12-0 halftime lead.
Three quick penalties came the Warriors way early in the second-half but a shoulder charge from Penrith's Waqa Blake pushed right wing David Fusitu'a into touch as he dived for the corner.
Right centre Peta Hiku had an unhappy night with some missed tackles and errors hurting the Warriors who played into the Panthers hands by attacking laterally rather than working it forward through the middle.
The Kiwi international fell off a poor attempted tackle on rampaging Panthers forward Kikau and then dropped out of the chase early before Phillips fed Blake to score their third try in the 53rd minute.
Kearney dragged Hiku from the field but it was all too late with the Panthers adding further tries through Kikau, Luai's second, and Harawira-Naera before Maumalo's late effort.
"It was tough to walk off the park with that scoreline," said captain Roger Tuivasa-Sheck.
"When we came out in that second half 12 points down we weren't too far off and we just had to fix a few things. But the way we started that second half, not getting to our kicks and not going set for set and getting in that grind, that's what let us down."
The Warriors will look to avoid a third-straight loss and regain some confidence with another tough away assignment against Brisbane at Suncorp Stadium next Sunday.
Panthers 36 (Tyrone Phillips, Jarome Luai 2, Waqa Blake, Viliame Kikau, Corey Harawira-Naera tries, Luai 5 cons, 1 pen)
Warriors 4 (Ken Maumalo try)
