bad river fold?

[lead24]

SB: $31.35
BB: $172.75
UTG: $48.65
CO: $49.25
Hero (BTN): $79

Pre-Flop: J/images/graemlins/heart.gif A/images/graemlins/diamond.gif dealt to Hero (BTN)
2 folds, <font color="red">Hero raises to $1.75</font>, SB calls $1.50, BB folds

Flop: ($4) 7/images/graemlins/heart.gif 8/images/graemlins/heart.gif J/images/graemlins/club.gif (2 Players)
SB checks, <font color="red">Hero bets $2.50</font>, SB calls $2.50

Turn: ($9) K/images/graemlins/club.gif (2 Players)
SB checks, <font color="red">Hero bets $6</font>, SB calls $6

River: ($21) 4/images/graemlins/spade.gif (2 Players)
<font color="red">SB bets $21</font>, Hero folds

Results: $21 Pot ($1.05 Rake)
SB mucked and WON $19.95 (+$9.70 NET)

very early in the session. I wasn't running PAHUD so no stats. I know my bet sizing was small but i'm interested in his river play. Is that a bluff enough to justify a call?

[Nemesis69]

Good fold. I think villian is slowplaying a monster all the way. I can't see him do this enough of the time with a busted draw to make it +EV.

[iheartponeez]

Get out. IF this is a bluff, you are not holding the right hand to snap it off on.

[ama0330]

This is fine IMO, maybe 7 on the turn but whatever.