I explained it before. I'd rather swing for the fences with what I perceive as TJ's upside than settle for the mediocrity I believe I'd get with any of the league's backups.
Maybe it's just me, but I missed the upside you are referring to. He can throw alright and run a little, no different from other also-ran QBs like Shaun King, Mike McMahon, Charlie Batch, Josh McCown. I've not once seen that dazzling performance where TJ showed himself to have that 320 yard/4 TD game in him. He's shown that maybe he can be the next Shaun King/Anthony Wright, but nothing more.
And if any backup could throw for 9/15 for 160 yards and a 1/2 td/int ratio, how many backups would you pick to start ahead of Vince Young?
Vince Young, from a leadership perspective [stats aside] doesn't belong in the same conversation with Tarvaris Jackson. He absolutely showed a higher ceiling in 2006, despite taking a step back during his sophomore season for a bunch of reasons. The problem is TJ has shown nothing, IMHO, that transcends meager statistics. He's shown he can perhaps "not lose" games. Whooopie. If our standards for a NFL QB in Minnesota have sunk that low, then I guess we'll just not rely on a QB to win games for the next 5-6 years.