Rookie Chris Borland of the Niners Retires

After only one season in the NFL, the San Francisco 49ers top tackler Chris Borland announced Monday that he's retiring due to concerns over head trauma.Borland, who is just 24, was going to replace 30-year-old Patrick Willis, who retired last week. According to San Jose Mercury News 49ers general manager Trent Baalke said in a statement, "While unexpected, we certainly respect Chris' decision. We will always consider him a 49er and wish him all the best."