They face Birmingham on Saturday after a 3-0 defeat by Tottenham at the DW Stadium following a late brace from substitute Roman Pavlyuchenko.
Wigan were left frustrated yesterday after replays showed that the opening goal by Jermain Defoe in the 27th minute was offside.
Kirkland said: "It is not even close. How he (the assistant referee) has not seen it, is hard to believe. It is two yards off.
"But these things happen in football. We have got to pick ourselves up and go again.
"We didn't play too well in the first half but if that effort is offside it may have been 0-0 at the break. It is bemusing.
"That is why you get frustrated. But now we have to concentrate on Birmingham now as we have 12 big games left."