49ers cut loss by releasing C Zuttah

The 49ers released Zuttah, 31, today to end a brief and disappointing tenure that began when they swapped sixth-round picks with the Ravens to acquire him in March. [...] Zuttah missed most of the offseason program with hamstring injury and never seriously challenged Kilgore in training camp. The 49ers filled Zuttah’s roster spot by signing linebacker Sean Porter, a 2013 fourth-round pick of the Bengals who has played in three career games. Porter played in two games last year with Jacksonville and 49ers defensive coordinator Robert Saleh was his position coach. Newsom update: A team spokesman said linebacker Donavin Newsom was “doing fine” and was scheduled to be released from Stanford Hospital on Thursday after he left the field in an ambulance with a concussion Wednesday. Shanahan said guard Joshua Garnett will have “clean-up” knee surgery Thursday and suggested he’s unlikely to be ready for the season opener. Garnett, a 2016 first-round pick, had been the starting left guard in training camp before he missed his first practice Saturday. Cornerback Dontae Johnson missed practice because of a concussion and will miss the preseason opener Thursday at Kansas City.