San Francisco 49ers running back Jerick McKinnon, foreground, carries against Dallas Cowboys defensive end Datone Jones (56), linebacker Jaylon Smith, center left, and linebacker Joe Thomas (48) during the first half of an NFL preseason football game in Santa Clara, Calif. McKinnon has injured his knee in practice and could be facing a serious injury.
San Francisco 49ers running back Jerick McKinnon, foreground, carries against Dallas Cowboys defensive end Datone Jones (56), linebacker Jaylon Smith, center left, and linebacker Joe Thomas (48) during the first half of an NFL preseason football game in Santa Clara, Calif. McKinnon has injured his knee in practice and could be facing a serious injury. Josie Lepe AP
San Francisco 49ers running back Jerick McKinnon, foreground, carries against Dallas Cowboys defensive end Datone Jones (56), linebacker Jaylon Smith, center left, and linebacker Joe Thomas (48) during the first half of an NFL preseason football game in Santa Clara, Calif. McKinnon has injured his knee in practice and could be facing a serious injury. Josie Lepe AP