Ivan Cleary has played down concerns around Jarome Luai's knee, after he left the field early in Penrith's 32-18 loss to Manly.
Luai was taken off with 12 minutes left after he stayed down midway through the first half when tackled in his own in-goal.
The five-eighth then fought on for the remainder of the match, before Cleary opted to withdraw him with Penrith down by 20 points.
The Panthers have the bye next week, and expect to have halfback Nathan Cleary back for their next match against Wests Tigers in a fortnight.
"He got a bit of a knock to his knee in the first half. At that point it wasn't worth him staying on," coach Ivan Cleary said.
"He's not too bad, but we'll see."
Luai's knee concern came as Penrith turned in one of their worst performances of their four-and-a-bit-year run at the top of the NRL.
After starting well, they were rolled through the middle either side of halftime and completed at less than 70 per cent for the last hour of the match.
They did face some adversity, with Manly centre Tolutau Koula awarded a contentious length-of-the-field try after Tommy Talau dropped an attempted intercept.
Penrith players believed the ball had been knocked on and most stood still as Koula ran away to score, before the bunker cleared the play and declared the ball had gone backwards.
The try put the Sea Eagles up 14-6 just prior to halftime, before they kicked away after the break via a Daly Cherry-Evans masterclass.
But even with the dropped ball in mind, the Panthers conceded they only had themselves to blame.
"The feeling was we thought it was a knock on," captain Isaah Yeo said.
"But our reaction off the back of that too (was poor). They scored a try, obviously disappointing. But after that there was just was just no control from us.
"We just didn't hold our hands up for long periods of time.
"Every time we finally start to get back in the arm wrestle a little bit, we'd make an error or give away a penalty."
