Mustain is a 21 year old senior who has thrown for 1,051 yards and 12 TDs in his career. I would say that qualifies him as a bust considering he was THE #1 QB coming out in 2006.
And to say he was "8-0" as a starter is technically true, but let's not spin that too much. He participated in exactly one quality win in that streak, and that was against Auburn, in which he threw a total of 10 passes.
In 2006, McFadden and Jones had over 3,000 yards of total offense. Mustain handed them the ball against
Utah State
Vanderbilt (2 pt win over 4-8 team),
Alabama (OT win over 6-7 team in which he went 7-22),
Auburn (ten passes),
SE Missouri St (he was 5-13),
Ole Miss (4-8 team),
La-Monroe (he was 7-18 with 2 picks),
South Carolina, but he only threw one pass, and it was a pick.
So yes, technically his team won 8 games that he started, but he had virtually nothing to do with the wins, as the scraped by in spite of him. Check the two games against SEMO St and La-Monroe, the two games where they opened it up a little. He was a combined 12 of 31.
I'm sure he's better now, just because he's no longer an 18 year old freshman, but his legend was built on the last quarter against USC because he completed a few passes and ran for a TD. But that was it, that was the peak of his career to this point.
If he ends up in the NFL I'll be shocked.