The first 12 years of his career he never won a playoff game, but in year 13 he's in the Super Bowl. You don't see players improve so much between year 12 and year 13 of their careers very often. He must have really changed his diet or his workout regimen or something in the offseason.
Of course, I'm being sarcastic. Lions fans like myself have known Stafford is an elite quarterback perfectly capable of leading a team to the Super Bowl for years. I've been beating that drum loudly since his rookie season. So much so in fact, that my friends have gotten sick of me talking up Stafford all these years.