Okposo was hurt when he and Senators forward Bobby Ryan didn’t see each other and collided early in the second period of Buffalo’s 4-3 shootout win at Ottawa on Thursday.
A head injury was an issue for Okposo last year when concussion-related symptoms nearly derailed his career. Okposo lost weight and had difficulty sleeping and spent a week in the hospital after sustaining a concussion during what he called a routine hit in practice.
The 11-year veteran is tied for third among Sabres with 38 points (11 goals and 27 assists) in 65 games this season.
The injury is the latest to affect the Eastern Conference’s last-place team. Leading scorer Jack Eichel has missed nearly a month with a sprained right ankle.
Buffalo hosts Vegas on Saturday.