Manly centre Jamie Lyon has been ruled out of action for 1-2 weeks as the struggling NRL premiers attempt to get their season on track.

There were fears Lyon could miss up to a month after injuring his knee as his team slipped to a third straight loss against Penrith on Monday night.

But the club said on Wednesday scans had confirmed a grade one medial ligament tear which would see him miss one or two matches.

Coach Des Hasler said the injury was a blow as Lyon had been in outstanding form.

He won't name a replacement for Sunday's clash with Newcastle at EnergyAustralia Stadium until the weekend.

"I am looking at the options we have available but won't speculate on what they are at this stage," Hasler said.

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