My source shows is is 19 0f 26 starts, 12 of which are with the Hawks, so that leaves 7? starts over the previous years.
"Wouldn't he have won a starting job at some point, no?"
You're correct, NO.!
Who was he backing up that he could have taken the job away from? Manning? Rivers? Wilson? He had no opportunity until this year.
Pete knew of his talent and abilities , he pursued him hard in the off season to keep him in Seattle, even though Wilson was still a Hawk at the time.
He didn't just get good over the last off season, all of his stops were learning and growing experiences, not everyone is a super star the first tear.
You're making him out to have been a total bust that just got lucky this year.