Can I fold this? My opponent was loose, but I wasn't sure if my opponent was aggressive or passive (probably somewhere in the middle, but this was the 4th or 5th hand so i didn't have much to go on). I really had no idea what to do on this river. I figured my opponent was calling on the flop and turn with something weak, as we had already played one hand where he won a lot of chips after calling with a weak draw on the flop and turn and hitting on the river.

PokerStars No-Limit Hold'em Tourney, Big Blind is t20 (2 handed) Poker Stars Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

BB (t1810)
Hero (t1190)

Preflop: Hero is Button with A, 9.
Hero raises to t60, BB calls t40.

Flop: (t120) J, A, 3 (2 players)
BB checks, Hero bets t80, BB calls t80.

Turn: (t280) A (2 players)
BB checks, Hero bets t140, BB calls t140.

River: (t560) 4 (2 players)
BB bets t1530 (All-In), Hero calls t910 (All-In).

Final Pot: t2380

bump. Sorry, maybe this hand is obvious, but I really had no idea what to do on this river (whether to call or fold).

His push looks really strong but there's a chance he could do it with a worse ace - also a chance he could have a big heart, missed his draw and is trying to bluff you off. I think it's more likely that you're behind though. Probably more likely he flopped a flush than hit a FH seeing as how he didnt raise to protect on the flop.

Not an easy situation - I think it's a fold but not an easy one.

yeah horrid situation. this is a situation where it is easy if you know your villain, but you might aswell flip a coin vs an unknown. i would not make a read off one hand of them calling with not much. loose passive villains love to slowplay.

i would call, but i think if you are being sensible it is a fold. it is not a bluff often enough and his non bluff range crushes you.

well i dont reckon it is a bluff often enough anyway: it is completely illogical as one.

At first, bet at least 2/3rd pot on the turn.
Like already said, a bluff is really unlikely here. He may do this with a worse ace, however, given you describe him as loose and somewhat passive, its more likely he has a better hand. I'd pitch it.

yeah and what with the 3 and the 4 on the table there are a limited number of worse aces

I think that at this level you should call. This guy could stack off here with a wide range imo. Any big pair, any big heart that missed its draw, often enough this is even king jack. Remember, play can really be erratic in elevens. the chance of straight up bluff is always somewhat signifficant (at least 10 percent here i think), and those other semi-bluffs are likely enough to make you plus EV here.

also - player dependent a lot of the time. You also played the hand kind of weak, never really sure of his strenght. i agree to a pot sized bet on turn - could simplify or prevent river wrecks like this.

peace.