Charteris and co remain in eighth place in the RaboDirect PRO12 but while Treviso remain three points adrift, Connacht have now closed the gap to four and Edinburgh to six.
And Charteris, who will leave the Dragons at the end of the season, has called his side to regain some pride in their final three matches, against Treviso, the Ospreys and Leinster.
"We were looking forward to building a good finish to the season but we are going to have to go away and re-evaluate that," the 29-year-old told the South Wales Argus.
"We need to have a good look at ourselves and say maybe we're not quite as good as we thought we were, particularly on the Connacht evidence.
"We have a week off and need to make sure we get two good wins in the next block against Treviso and the Ospreys.
"It was the polar opposite of our win at Edinburgh the previous week.
"We were very clinical and hardly missed any tackles; that's how you get a good away win.
"Coming home that should be all there but those little things let us down against Connacht.
"We missed more tackles in the first half that we have all year and you can't get away with that at this level."
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