Bowers has not taken part in any drills since undergoing meniscus surgery last week, and his absence was confirmed again during Thursday's practice session.
Head coach Klint Kubiak reiterated his optimism earlier in the week that Bowers might be cleared to practice, but emphasized that Friday will be the last chance for the player to rejoin the roster before the upcoming matchup with the Chargers.
In Bowers' continued absence, veteran tight end Michael Mayer is expected to assume the primary role at the position; Mayer recorded six receptions for 32 yards in the Raiders' 31‑28 victory over the Miami Dolphins last Sunday.
The practice also saw cornerback Darien Porter miss his second consecutive day due to a foot injury, while quarterback Aidan O’Connell was absent for personal reasons.
Running back Ashton Jeanty, who was dealing with an ankle issue, was listed as a full participant in Thursday's session, indicating his readiness for the upcoming game.