Hi guys. I played this hand against an aggressive reg.
Since he checked the turn i I decided to lead the river to get value from weak Ax that would just check and from a weaker pair.
I tried to figure out a range he could play like this but the only thing that i could thing about was something like the nut flush, since he checked the turn (even though he is aggressive and i think most times he will bet it) and a smaller flush would bet for protection, 42 that binked the river or A3. his line just seemed so weird that i thought that he didn't have enough bluffs for me to call.
PokerStars - 10/20 NL (2 max) - Holdem - 2 players
Hand converted by PokerTracker 4

SB: 71.25 BB (VPIP: 80.79, PFR: 68.66, 3Bet Preflop: 28.02, Hands: 790)
Hero (BB): 78.75 BB

SB posts SB 0.5 BB, Hero posts BB 1 BB

Pre Flop: (pot: 1.5 BB) Hero has 9 Q

SB raises to 3 BB, Hero calls 2 BB

Flop: (6 BB, 2 players) A Q 9
Hero checks, SB bets 4.2 BB, Hero calls 4.2 BB

Turn: (14.4 BB, 2 players) 5
Hero checks, SB checks

River: (14.4 BB, 2 players) 3
Hero bets 6.5 BB, SB raises to 64.05 BB and is all-in, fold,

Check raise flop. River bet too weak, should bet toward 10-14BB . As for the river close spot but I would lean towards folding, I'd like to call on this spot with at least A9 without other reads on the player.

Please do not kill me if I make a mistake in the calculations.

64.05 - 7.5 - 6.5 = 50bb to call
50/(14.4 + 6.5 + 64 + 50) = 50/134 (37%)

We should win more than 37%.

hand: Q9
board: AQ953

27 combination lose:
Q3 (6)
93 (6)
95 (6)
53 (9)

114 combinations win:
flush (55)
AA (3)
QQ (2)
99 (2)
55 (3)
33 (3)
AQ (6)
A9 (6)
A5 (9)
A3 (9)
42 (16)

27/(114+27) = 19% (all combinations)
27/(59+27) = 31% (without flush)
27/(37+27) = 42% (only 33, A5, A3, 42)

In the latter case, I left only 33, A5, A3, 42. This is the most ideal variation for us. But in reality he'd bet with all the sets, because you can have a flush draw on the turn or hands weaker. I think that the flush is unlikely, 'cause why he'd make the check behind? Even if he doesn't have a flush, then you should win in 31%, which isn't enough to call. I like your bet size on the river. 'cause unlikely that you've a weak hand. If you bet less, he could raise with air, but not all-in. So mathematically you did everything right. Even full donkeys won't be so bluffing.