Seidenberg left Boston's 5-0 home win over Ottawa Friday with a leg injury that did not initially appear to be serious. A follow-up examination revealed tears of the medial collateral and anterior cruciate ligaments.
The 11-year veteran -- who signed a four-year contract extension worth $16 million before the season -- is likely to miss 6-to-8 months.
Seidenberg will finish the season with one goal and 10 points in 34 games.
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