David Mooney scored the game's only goal after half-time and, although visitors had defender Ryan Dickson sent off in the 87th minute for a second yellow card, Latics were unable to launch a fightback.
"We're looking for a top-half finish and here we missed a big opportunity," said Dickov.
"We didn't have the guile to break them down and switched off defensively too often, so I'm very disappointed.
"We are much better than that, but our concentration levels let us down and our decision-making wasn't good enough.
"Their keeper made a couple of good saves but we didn't have enough quality and we conceded a poor goal."
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