Odds of single opponent having pair or better?

[Isles]

I don't know how closely you can get to this answer [img]/images/graemlins/smile.gif[/img]

If you are playing against 5 opponents, and you raise preflop, and get one caller, what are the odds that this single opponent has a high pair or better by the river?

High pair can mean top pair on a low board, I simply mean a legitimate reason for someone to call you down.