"I've proven them wrong before," Rivera said in an interview published by the Associated Press.
Rivera said he considers his status "day-to-day." He speaks with some authority on the matter as this is his third torn MCL in less than a year. He injured both knees last season and underwent off-season surgery on his right knee.
This time, the injury was magnified by muscle damage caused when Carolina defensive tackle Kris Jenkins rolled up on Rivera's leg in the first quarter of the Packers' 20-7 loss at Lambeau Field Saturday night.
"When I've torn MCLs before, they just pop and then I stand up and I realize something's not right," Rivera said. "This one, I felt pain right away and I feared the worst. I thought it was an ACL or something. I feared my season was over.
"So this is great news today. I can deal with what 've got. I'm going to do some serious rehab and get back on the field," he said.
Bill Ferrario is likely to replace Rivera in the preseason finale vs. Tennessee Thursday night.