USC finished with a top-ranked 2015 recruiting class, but started 2016 with a miss.
Quarterback Shea Patterson, from Shreveport, La., on Tuesday announced his commitment to Mississippi via an Internet livestream.
Patterson, who USC offered last July, is regarded as a top prospect in the class.
In two seasons at Calvary Baptist High, he passed for 72 touchdowns and seven interceptions.
Patterson was once committed to Arizona.
USC has offered Santa Margarita's K.J. Costello and Malik Henry, who transferred from Westlake to IMG Academy in Florida.
Henry has verbally committed to Florida State.