The Sabres announced Thompson had the operation on Tuesday and will require between five and six months of recovery time. Thompson was initially projected to miss three to five weeks before team doctors determined he required surgery.
The third-year player was hurt in the final minutes of a 4-1 loss at Chicago on Nov. 17. It was Thompson's first NHL game of the season and came shortly after being promoted from AHL Rochester.
Thompson had seven goals and five assists for 12 points in 65 games with Buffalo last season before being demoted to the minors. The 2016 first-round draft pick was acquired by the Sabres in a multiplayer trade that sent center Ryan O'Reilly to St. Louis in July 2018.
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