[ QUOTE ]
he doesn't seem to have a decent showdown hand after he limped UTG.

[/ QUOTE ]

I think you are putting too much emphasis on this simple fact. Yesterday I raised flop from the CO with AQo, had to abandon it on the flop and someone won with a freak fullhouse that he filled on the turn and river with 84o from UTG or something. Then he actually posted in the chat-window: "You see? That's why it's silly to raise pre-flop."
People call down with TPTK and straights. Why do you think he has no hand at all? Despite it is 6max, he might even choose to limp with a small PP.
I don't understand why you are so confident about that. Especially without reads.

Regards