The talismanic lock and NSW captain pulled up sore after making a tackle and left the field during the final 10 minutes of the first half in Auckland.
If scans confirm a pectoral tear, Yeo could miss the remainder of the Panthers' push for a fifth premiership in six seasons.
"It doesn't look great," Panthers coach Ivan Cleary said of Yeo's injury.
"Obviously Yeoy's a big loss and hard to replace, but that's how it goes, if that's the case, we'll have to (replace him)."
At the very least, Penrith will be left to fend off their minor premiership challengers without Yeo, a task that already became more difficult with Friday night's loss.
First on the ladder since round four, Penrith may only be two competition points ahead of fourth place by the end of the weekend.
The Warriors sounded the loudest warning shot yet that a first premiership could be on the cards in 2026, with Luke Metcalf excelling in his first NRL game since April.
"They're definitely going to be a handful as the season goes on," Cleary said of his former club.
The hosts dominated Penrith for a 22-0 second-half lead, before star halfback Nathan Cleary helped cut the deficit to 10 points in the final 15 minutes.
But it was too little, too late as out-of-favour Metcalf stepped inside to score his second try and confirm the result in the final five minutes.
Making matters worse for Penrith, Paul Alamoti could face suspension for up-ending opposite centre Leka Halasima in the first half and being sent to the sin bin.
While Alamoti was missing, Halasima set up the Warriors' third try, bumping through Cleary on a ferocious break down the field then throwing a one-handed offload to Chanel Harris-Tavita.
But St George Illawarra's prized recruit Metcalf shone brightest as he replaced the injured Te Maire Martin for only his third NRL game of the year.
After Erin Clark waltzed over for a very soft opening try, Metcalf backed Kurt Capewell up and gave the hosts a 12-0 lead.
Just after halftime, Dallin Watene-Zelezniak tapped Metcalf's kick back for Charnze Nicoll-Klokstad, who gave the Warriors their fourth four-pointer.
Metcalf will retain the halfback jersey in round 24 as Martin misses between two and four weeks with his hamstring issue.
"Particularly the last five, six weeks, (Metcalf) has strung some really good footy together," said Warriors coach Andrew Webster.
"I'm just rapt with all our halves."
It took Penrith until the 67th minute to crack the scoreboard, with Cleary supporting Izack Tago and Tom Jenkins on a break down the left edge.
He popped a no-look pass up for Jaxen Edgar to score and the Panthers thought they had a third try when Alamoti regathered his bomb shortly thereafter.
But Liam Martin was ruled offside on the kick chase, before Metcalf's second try confirmed the hosts' win.
"I thought we played really good for 70 minutes, there was a 10-minute period where we lost our way a little bit," Webster said.
"(But) I'm really proud of the boys tonight."
