22 - how big a hand to fold here?

[gumpzilla]

Stars 22. The chip situation: chip leader has 5300 chips, I have 4100, three players with 1300-1500. I'm in the SB, and chip leader is the BB. I've been pretty aggressive, but built up most of my chipstack picking off a bluff on a board with four to a flush from one of the now short-stacks. I pick up A [img]/images/graemlins/heart.gif[/img] 9 [img]/images/graemlins/heart.gif[/img], it's folded to me.

gumpzilla: raises 225 to 375
Villain: calls 225
*** FLOP *** [3c 8s 5s]
gumpzilla: bets 600
Villain: calls 600
*** TURN *** [3c 8s 5s] [As]
gumpzilla: checks
Villain: bets 4355 and is all-in

I don't think he has a flush. I have 3100 behind, there's basically 5000 in the pot. What's the smallest A you call with here? If you won't call with an A, are you firing a blocker on the turn instead?