[BluffTHIS!]

You would actually rather the 9 wasn't there and a higher card instead so that if you make a straight with someone on the turn he isn't freerolling on you with a higher card to make a better straight on the river. And you are out of position which means that a smart opponent with virtually the same hand who makes a straight with you on the turn and just smoothcalls your bet will now be in perfect bluffing position if the board pairs or a backdoor flush comes which you don't have, and he can try to get you off a split.

And if you meet resistance with your flop bet, you would also prefer to be against a set that could not split with you on certain straights, and so that you avoid the disaster of getting allin with 9876 where 2 broadway cards come on the turn and river and he takes it down with a pair of 9s (I've seen 10K+ pots go like this in both live and online play where two slightly different wraps/draws collided). All of which shows any draw plays better in position, getting a cheap or freeplay in the blinds notwithstanding. Of course if a diamond made your straight on the turn then you usually would be the one freerolling against another similar hand.

This would be a great hand to have headsup versus a preflop raiser with aces, but could be a potential trap in an unraised pot out of position if you are not very careful and cannot read someone's play well enough to know when they are bluffing on the river when a scare card comes or when they have in fact made a better straight or flush/full.