Darren Edwards' side kept hold of eighth place but those below them, including Treviso, are breathing down their necks.
And Smith has called on his side to right their wrongs when they return to action in front of their home fans on Friday.
"The performance simply wasn't good enough against Connacht," Smith told the South Wales Argus.
"There was nothing that we could take from that game.
"It was one of those games where from 1 to 15 we couldn't get into it and by the time we woke up it was too late and we had left ourselves too much to do.
"If we had played badly and scrambled the points then at least you could say 'a win's a win' but we were left with nothing.
"But that performance didn't deserve anything and we are determined to put that right against Treviso. We know that we need to put in a big performance for the fans.
"It was massively disappointing against Connacht but that's professional sport for you. If it was easy then it wouldn't be so great when you do win."
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