4/180 - UTG All In From a Short Stack

[All_In_Olly]

UTG raises obviously signify strength usually.

But when a short stack goes all in UTG I sometimes find he's actually got a huge range - not just because of his M, but because he wants to get it all in before he goes through the blinds again.

Here the villain has an M of ~5.5, still, A9 is a marginal holding, is it good enough?
If not, what's your minimum here?

Blinds are 300/600, villain is 17/9 VPIP/PFR over 200, so is on the tightish side.

PokerStars No-Limit Hold'em Tourney, Big Blind is t600 (7 handed) internettexasholdem.com

SB (t14274)
Hero (t31018)
UTG (t6671)
MP1 (t23025)
MP2 (t6647)
CO (t15519)
Button (t19301)

Preflop: Hero is BB with A[img]/images/graemlins/diamond.gif[/img], 9[img]/images/graemlins/diamond.gif[/img].
<font color="#CC3333">UTG raises to t6621</font>, <font color="#666666">5 folds</font>, Hero ?