The Canada international has won 17 caps and started two of his country's World Cup pool games earlier this season.
The Ospreys said that Hassler's operation was to repair what they described as an "ongoing" shoulder problem.
" Jeff has had an ongoing shoulder problem that we've had to manage since his return from the Rugby World Cup last autumn which, although not affecting his rugby, has impacted on aspects of his gym-based preparation," Ospreys medical performance manager Chris Towers told ospreysrugby.com.
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" In light of him being unavailable this weekend anyway due to a short-term soft tissue injury, we have elected to repair the shoulder through surgery, giving him the maximum recovery time and the best preparation for next season."
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