O'Brien (lower body) was placed on injured reserve on Sunday.
O'Brien was held out of Seattle's lineup for their preseason contest Thursday. The 19-year-old center was exceptional with OHL Brantford in 2025-26, where he compiled 28 goals and 93 points across 53 regular-season games. Once O'Brien is ready to go, the Kraken will have to decide whether they want to try him out with their current roster, or push off his NHL debut by potentially optioning him to AHL Coachella Valley.