The San Francisco 49ers were absolutely ravaged by injuries last season, which played a massive role in their disappointing 6-11. And once again this summer, the 49ers are once again experiencing medical issues.

The San Francisco 49ers continue to manipulate their roster, as they deal with several injuries at key positions in the preseason.

The 49ers announced a handful of roster moves on Wednesday. They have signed offensive lineman Michael Dunn and wide receiver Malik Knowles to their 90-man roster. They released defensive lineman Demone Harris and waived running back Corey Kiner with an injury designation in corresponding moves.

The 49ers have committed to Brock Purdy with a big extension. But the key to that deal is the guy standing behind him in the backfield.

There's no clarity yet on which quarterback will start for the San Francisco 49ers in their final preseason game.

The 49ers wisely have some key veterans, most prominently Nick Bosa, Christian McCaffrey and Trent Williams, on schedules designed to keep them fresh and out of the fray from time to time. Quarterback Brock Purdy is a leader in a more reserved, analytical way. Deommodore Lenoir is stepping up to push the secondary.

"If the 49ers want to lighten Christian McCaffrey's workload, they must add a durable running back to the rotation," Moton wrote. "Robinson can grind out yards between the tackles, which would allow McCaffrey to stay fresh for the length of the regular season."

This is a significant blow to the 49ers' RB room since Taylor had secured a spot as a reliable third or fourth option who contributed on special teams. He posted a career-high 109 yards on 17 carries in San Francisco's Week 18 loss to the Arizona Cardinals last season.