49ers LG Aaron Banks avoids serious injury

49ers left guard Aaron Banks left Sunday Night Football after 39 of 71 plays. The 49ers were concerned, but the MRI delivered good news.Coach Kyle Shanahan said Monday that Banks avoided a serious injury.Banks has a mild shoulder strain, with a day-to-day prognosis."Any time it's the biceps, we were obviously nervous about it," Shanahan said, via David Bonilla of 49erswebzone.com. "It's still an injury, but not as bad as it could have been."Jon Feliciano replaced Banks in the lineup in the third quarter.Defensive end Drake Jackson is fine after a collision with teammate Nick Bosa late in the first half. "He got the wind knocked out of him," Shanahan said.Running back Elijah Mitchell, who has missed the past two games with a knee injury, still is day to day, according to Shanahan.