Joe Staley will get MRI on knee

SAN FRANCISCO -- The San Francisco 49ers could play a crucial NFC West game against Seattle next week without two standout offensive linemen.

Left tackle Joe Staley left Sunday's 23-13 win over St. Louis with a right knee injury. According to a source close to the situation, the initial belief is Staley suffered a sprained MCL. He must get an MRI on Monday before the final determination. Staley was on the 49ers' sideline wearing a brace in the second half.

If Staley, indeed, has an MCL sprain, he will likely miss next week's game against the Seahawks. Standout guard Mike Iupati suffered the same injury two weeks ago at New Orleans. He hasn't played since, but may be getting close to returning.

When Staley was hurt, right guard Alex Boone moved to left tackle and second-year player Joe Looney replaced Boone. Adam Snyder has replaced Iupati the past two games. This will likely be the same lineup against Seattle if Staley and Iupati are out.

Until Iupati was hurt the San Francisco lineup was intact since the start of the 2012 season.

While the line play wasn't perfect after Staley was hurt, the unit did a fine job against the Rams, who have one of the better defensive fronts in the NFL.

"It's not easy to replace those guys," 49ers' fullback Bruce Miller said of Staley and Iupati. "But from my vantage point, they did great."