Niners' McCaffrey sits out Tue. practice ahead of Seahawks tilt - ESPN

SANTA CLARA, Calif. — The San Francisco 49ers began preparation for Saturday's showdown against the Seattle Seahawks with two of their best players — left tackle Trent Williams and running back Christian McCaffrey — sitting out Tuesday's practice.

Though Williams and McCaffrey don't normally participate in the first practice of the week because of veteran rest days, the pair showed up on Tuesday's participation report with actual ailments. In Williams' case, it was an injured right hamstring suffered in Sunday's win against the Chicago Bears. McCaffrey was a new addition because of what coach Kyle Shanahan described as back stiffness.

Of the two, Williams' status for the game against Seattle appears to be more tenuous. Shanahan said there isn't yet a determination on how much time Williams could miss after injuring the hamstring on the first play of last week's game. He did leave the door open for Williams to play against the Seahawks, though that will be difficult, especially on a short week.

«Not sure how long [he'll be out],» Shanahan said. «He's got a shot for this week.»

McCaffrey was more adamant about his status, saying the back issue is «not serious» in his weekly meeting with the media. Shanahan indicated McCaffrey has been fighting the back stiffness since the Dec. 14 game against the Tennessee Titans.

«I know he battled it hard that week, but I haven't heard anything about it since,» Shanahan said. «It might have stiffened up in the game, and it was sore from Sunday night, so that's why we've got him on here today.»

In better news for the 49ers, tight end George Kittle was a limited participant in Tuesday's practice after missing last week with a sprained left ankle. Kittle injured the ankle against the