The Sharks moved quickly Thursday to replace longtime goalie Evgeni Nabokov after telling him last month they wouldn't re-sign him.
Niittymaki spent last season in Tampa Bay after playing four full NHL seasons with the Philadelphia Flyers. The Finnish goalie went 21-18 with a 2.87 goals-against average last year.
Niittymaki joins Thomas Greiss and minor-leaguer Alex Stalock in the Sharks' goaltending competition.
Nabokov has been the Sharks' starting goalie for most of the past decade, but San Jose decided he was too expensive. The Sharks instead signed forwards Patrick Marleau and Joe Pavelski to long-term contract extensions.
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