"He's got a bit of a tear and he'll see a consultant to get an accurate view," Llanelli Scarlets head coach Wayne Pivac told the BBC on Wednesday. "With any luck it's just a rehab job."
The injury will probably sideline the 24-year-old for 10 weeks, with Wales starting their Six Nations campaign against Ireland in Dublin on Feb. 7 and ending against Italy on March 19.
Ball, whose family emigrated to Australia when he was a teenager, has 15 caps and last played for Wales in a 54-9 World Cup victory against Uruguay at the Millennium Stadium in September.
Ball said on Twitter that he was "absolutely gutted" by the news but would "be back bigger and stronger in the New Year".
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(Reporting by Alan Baldwin, editing by Ed Osmond)
