[sy_or_bust]

Tricky...you face a strong likelihood of being crushed or sandbagged combined with a flush redraw you don't have. To me, it looks like a realistic best case scenario is when CO holds a pair + A[img]/images/graemlins/diamond.gif[/img] and UTG has nothing. I think many more instances will have you crushed, drawing to one out or less.

If CO will make this move with the pair + redraw, then I call and plan to call a non-diamond river. This player would need to play hands like KJ[img]/images/graemlins/diamond.gif[/img] this way for me to call. If I think the above is unlikely, I fold.

UTG helps a ton here when you call. If you assume he is always in 2nd or 3rd place when you showdown (i.e. not a threat), you're getting better odds on a calldown.