The 26-year-old had been due to join up with Fiji for the autumn games with Scotland, Ireland and Romania after the game.
However, the back row is now set for five weeks on the sidelines and will remain at Sixways for treatment after injuring ligaments in his left knee. The club is also awaiting test results on Talei's left shoulder.
Director of Rugby Mike Ruddock said: "It is disappointing news for Netani, particularly on a personal level as he was due to represent his country in the autumn. It's most unfortunate on the basis that he is a proud Fijian and always wears his jersey with great pride.
"On Saturday we saw Netani hit real top form with a series of powerful carries and offloads in and around the contact area. He had his best game for us this season and so he will be disappointed to have missed out on the Fijian team just as he was hitting his best form.
"From our perspective, this doesn't change things that much for us in that we were expecting to be without Netani for a number of weeks and we are hopeful that Kai Horstmann will pass a fitness test in time to play against Bath for the Warriors on November 20."