Word comes out of the Trojan camp today that second-string QB Mark Sanchez has a hairline fracture in his right thumb (that’s on his throwing hand) and will miss the next 3-4 weeks. Mike McDonald moves up officially to become John David Booty’s backup, for now, although freshman Aaron Corp got a lot of extra work today in practice. (More on that in tonight’s practice roundup.)

Scott Wolf also reports that OL Sam Baker missed practice with what was described as a “rib strain,” with more details hopefully forthcoming. Running backs Joe McKnight (sore neck) and Emmanuel Moody (knee bruise) are also a bit banged up, but should be fine.

Injury Updates (Scott Wolf)