Wilson told the San Jose Mercury News Hertl will have the knee operated on next week, with a timetable for a return to be determined then.
The GM had earlier indicated Hertl would likely miss one month, but that assessment now appears optimistic.
The rookie sensation sustained the damage on a knee-on-knee collision with Dustin Brown of Los Angeles during Thursday's 4-1 loss to the Kings.
Hertl has notched 15 goals and 10 assists over his first 35 NHL games.
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