USC backup QB Mark "The Dirty" Sanchez will be sidelined for 2-4 weeks after injuring the thumb on his right (throwing) hand at Sunday night's scrimmage. The redshirt sophomore has a "hairline crack" and there is a chance that he will miss the season opener vs. Idaho. Third-team QB Mike McDonald, who doubles as the holder on placekicks, will take over the backup role behind fellow senior John David Booty. Remember, McDonald converted a fake FG for a TD vs. Washington last season when he hit WR Steve Smith all alone on the sideline. Though McDonald is a savvy veteran and knows the offense well, he needs to take all the reps he can in practice to get ready for the start of the season. Freshman Aaron Corp is young and inexperienced, and Mitch Mustain must sit this season out after transferring from Arkansas. Fortunately, USC has a bye week before traveling to Lincoln, Nebraska in Week 3 to take on the Cornhuskers. The Idaho game is expected to be a rout, and would provided a good opportunity for Sanchez to receive valuable playing time. Sanchez needs to get a head start on his competition for the 2008 starting QB job. Let's wish him a full and speedy recovery.