The Warriors worst fears have been eased with confirmation that Shaun Johnson's knee injury is not as bad as expected although he is still facing between six to eight weeks on the sidelines.

MRI scans today revealed Johnson ruptured the posterior cruciate ligament in his left knee during the Warriors 34-22 NRL defeat to Penrith on Friday night.

The initial diagnosis suggested the 26-year-old may have suffered season-ending damage to the anterior cruciate ligament, which would have been a major blow to both the Warriors' slim NRL finals hopes and New Zealand's ambitions for the season-ending Rugby League World Cup in November.

"This is a much better outcome than we had expected," said Warriors team doctor John Mayhew.

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"We had believed the injury was likely to be an ACL but scans have indicated this isn't so and Shaun won't need surgical intervention to repair the injury."

Johnson sustained the injury midway through the second-half against the Panthers when he fell to the turf while chasing an Issac Luke kick before being assisted from the field.

His importance to the Warriors was underlined by the fact they were still in command with a 22-18 lead before he departed, only to concede three late tries in his absence as the Panthers roared back to claim an impressive victory.

Johnson now remains a chance of returning for the Warriors final regular season game against Wests Tigers in Sydney on September 3, and in line to take his place for the Kiwis at the World Cup co-hosted by New Zealand and Australia.

However, the decision on whether Johnson is rushed back for the Leichardt Oval clash may depend on whether the Warriors are still in the NRL finals race.

Nine-game rookie Ata Hingano is again expected to replace Johnson and partner five-eighth Kieran Foran in Saturday's crucial away clash against North Queensland in Townsville.

With the Warriors currently occupying 11th spot on the NRL ladder on 18 points and four points outside the top eight, they need to win at least five of their remaining seven games to keep their playoff hopes alive.

Should the Warriors miss the finals for a sixth straight season, Johnson would have a further seven weeks to properly recover and condition himself ahead of the Kiwis World Cup opener against Samoa at Mt Smart Stadium on October 28.

His presence will be all-important to the Kiwis hopes of redemption after they managed just one win in their last six tests since coach David Kidwell took the reins prior to last year's Four Nations tournament.

With former New Zealand captain Jesse Bromwich and senior forward Kevin Proctor banned from World Cup selection after their involvement in a drugs scandal following this year's Anzac test loss to Australia in Canberra, the Kiwis cannot afford to be without their main playmaker.