Matt Barrows is reporting 49ers left guard Mike Iupati suffered a sprained left MCL in the 49ers Week 11 loss to the New Orleans Saints. Barrows also tweeted that Iupati was "likely to miss" Monday's game against Washington.
Iupati suffered the injury late in the third quarter. He left the previous week's game briefly with a leg injury, but was back the next series. He was a full participant in practice last week, and was listed as probable for the Saints game. Given this news, it is unlikely he'll even practice this week. The first injury report for Monday's game comes out on Thursday.
If Iupati is unable to go next Monday, Adam Snyder would seem likely get the start in his place. Daniel Kilgore can also play inside, but Snyder came on at left guard when Iupati went down. We'll get a better idea of this when the 49ers return to practice later in the week.
The 49ers also have Joe Looney on the roster, although he has been active all season. If Iupati is inactive this week, I would hope Looney would get activated. We'll see.