The 49ers see Warner's hamstring injury as "short term" following Monday's MRI, Jeremy Fowler of ESPN.com reports.
Warner left Sunday's win over the Vikings early and will undergo further testing to determine the exact severity of his injury. The starting middle linebacker, who has 92 tackles and three passes defended this season, remains vital to a 49ers defense which may once again be without fellow LB Dre Greenlaw (groin).