Compensating for the likely injury-enforced absence of Warriors star Shaun Johnson is a near-impossible task, his halves partner has admitted.

Kieran Foran could only watch on in horror as Johnson, with his side up 22-18 in the 62nd minute of Friday's NRL clash with Penrith, buckled over chasing an Issac Luke chip-kick and visibly grimaced in pain.

He limped off and the Warriors slumped to a 34-22 defeat.

As both the Warriors and Kiwis playmaker-in-chief, hearts will be in mouths until Johnson's condition is made clear.

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The 26-year-old will undergo knee scans on Saturday, with an announcement from the club expected at some point on Sunday or Monday.

Should Johnson's worst fears be confirmed, his 2017 campaign - including the Rugby League World Cup - could be over.

"You can't replace a guy like that," Foran said.

"It's going to come down to the leadership group, everyone stepping up a notch and collectively, everyone will (also) just have to play that little bit better,"

"He was pretty disappointed (in the sheds). It's hard to take any injury, let alone one like that, where it happens all of a sudden."

After a 2016 season marred by niggling injuries, Johnson has mostly looked the goods this year and benefited from Foran's composed presence.

Johnson has 16 try assists this year - the equal highest in the competition to date - as well as nine line breaks and four tries.

Foran admitted that, after Johnson was replaced by young gun Ata Hingano, everything fell apart for the Warriors.

They now need a minimum of five wins from their remaining seven matches to stand a chance of qualifying for their first finals since 2011.

"It's huge to lose a player of Shaun's calibre out there in a tight contest," Foran said.

"With 18 minutes to go, it's pretty difficult to adapt. In saying that, we should've done a better job.

"We were still ahead at that point, and we should've been able to close the game out. We just allowed them to break our line too easily."