Ultimate Bet No-Limit Hold'em, $.50 BB (9 handed) converter

Hero ($34.35)
SB ($25.80)
BB ($17.50)
UTG ($56.85)
UTG+1 ($33.65)
MP1 ($77.10)
MP2 ($41.60)
MP3 ($48.25)
CO ($33.05)

Preflop: Hero is Button with A, 7.
4 folds, MP3 calls $0.50, CO calls $0.50, Hero calls $0.50, SB completes, BB checks.

Flop: ($2.50) A, K, 8 (5 players)
SB bets $0.5, BB calls $0.50, MP3 calls $0.50, CO folds, Hero raises to $4, SB calls $3.50, BB folds, MP3 folds.

Turn: ($11.50) 4 (2 players)
SB checks, Hero bets $6, SB calls $6.

River: ($23.50) K (2 players)
SB bets $15.3 (All-In), Hero folds.

How often is this just a busted draw or a hand I can beat? In my notes I have him pegged as kind of a call station.