The San Francisco 49ers are basking in the glory of their upset win over the Green Bay Packers in the NFC Divisional Round. While the team is ecstatic to have advanced to the next round, head coach Kyle Shanahan provided something of a wake-up call for Niners fans on Monday. Via Matt Maiocco, Shanahan revealed a concerning injury update on star offensive lineman Trent Williams, which will have Niners fans worried.

Shanahan revealed that Williams was dealing with an ankle sprain, before adding that “there are some old components” to it. Williams has dealt with ankle injuries in the past, and Shanahan seems to think this is an extension of a past ailment.

Williams was seen limping off the field in the waning moments of the 49ers’ win over the Packers on Saturday. It was the second time in the game cameras had shown Williams walking with a significant limp, but the offensive lineman toughed out the pain in order to help his team earn a win.

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After the game, Williams underwent X-rays on his ailing ankle which came back negative, indicating that it was just a sprain, rather than a fracture. While that’s certainly encouraging, Shanahan revealed that the team remains unclear on whether Williams will be good to go against the Rams in the NFC Championship.

Obviously, the loss of Williams, who is one of the NFL’s premier offensive linemen, would be a significant blow for the 49ers as they look to reach their second Super Bowl in three years. Shanahan will surely provide further updates on the 33-year-old as the week progresses, but for now, his status is up in the air.