How to proceed? Slowplay or raise?

[Lufcmot]

[ QUOTE ]
As you wish. My regret here is that I let 'em up on the river (fear of the straight I guess)

SB showed down 22, UTG+1 showed down with A9o.
I don't know what Button had.

PokerStars 0.25/0.50 Hold'em (9 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Preflop: Hero is BB with A[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/club.gif[/img]. MP3 posts a blind of $0.25.
<font color="#666666">1 fold</font>, <font color="#CC3333">UTG+1 raises</font>, <font color="#666666">3 folds</font>, CO calls, Button calls, SB calls, Hero calls.

Flop: (11 SB) 5[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/spade.gif[/img], 2[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(5 players)</font>
<font color="#CC3333">SB bets</font>, Hero calls, <font color="#CC3333">UTG+1 raises</font>, CO folds, Button calls, SB calls, <font color="#CC3333">Hero 3-bets</font>, <font color="#CC3333">UTG+1 caps</font>, Button calls, SB calls, Hero calls.

Turn: (13.50 BB) 3[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, <font color="#CC3333">Hero bets</font>, UTG+1 calls, Button folds, SB calls.

River: (16.50 BB) K[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, <font color="#CC3333">Hero bets</font>, UTG+1 calls, <font color="#CC3333">SB raises</font>, Hero calls, UTG+1 calls.

Final Pot: 22.50 BB

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What I see is that this hand was slightly different, in terms of that you had the pf raiser behind you. Your call is much "safer", you could assume that it was gonna be raised. And why no raise pf?