Kostin (upper body) was put on injured reserve Saturday, per Curtis Pashelka of The San Jose Mercury News.
Kostin was injured during Thursday's 4-3 win over St. Louis, making him ineligible to play until at least Dec. 21 against Edmonton. He has a goal, four points, 25 PIM and 63 hits in 20 appearances in 2024-25. Will Smith (upper body) was activated off IR in a corresponding move.