5/10 facing strange river bet

[shmahappens]

Villain is 28/23/3.5 after a small sample size. Only hand of note he minraised flopped nuts vs PF raiser then pushed (overbet) a turn brick.

Full Tilt Poker - No Limit Hold'em Cash Game - $5/$10 Blinds - 6 Players - (LegoPoker Hand History Converter)

SB: $1,210.00
Hero (BB): $919.00
UTG: $2,127.00
MP: $1,507.00
CO: $1,005.00
BTN: $2,158.00

Preflop: Hero is dealt 9[img]/images/graemlins/diamond.gif[/img] 7[img]/images/graemlins/heart.gif[/img] (6 Players)
4 folds, <font color="red">SB raises to $30.00</font>, Hero calls $20.00

Flop: ($60) 5[img]/images/graemlins/spade.gif[/img] 6[img]/images/graemlins/club.gif[/img] K[img]/images/graemlins/spade.gif[/img] (2 Players)
<font color="red">SB bets $30.00</font>, <font color="red">Hero raises to $82.00</font>, SB calls $52.00

Turn: ($224) 8[img]/images/graemlins/spade.gif[/img] (2 Players)
SB checks, <font color="red">Hero bets $144.00</font>, SB calls $144.00

River: ($512) J[img]/images/graemlins/club.gif[/img] (2 Players)
<font color="red">SB bets $70.00</font>, <font color="red">Hero ?