Rovers - who saw John Marquis sent off for two bookable offences - are now winless in their last four League One matches but have held onto sixth spot with their rivals for a play-off place unable to take advantage.
They lacked their typical attacking energy and relentlessness at Wimbledon, as they have done for lengthy spells during their recent run.
And McCann believes the reality of their situation may have had a negative effect - something he is determined to put right quickly.
"There's no complacency but there may be a little bit of fear," McCann said.
"Maybe it's a case of 'there's 11 games to go and we're in this position.'
"The group were 15th in the league last season so maybe they're thinking a little bit like that.
"We'll get them back.
"We're in sixth place and we want to be better than that.
"We didn't deserve anything out of the game possibly because of the first half display really.
"Forget the sending off, the first half display was not good enough from us.
"We didn't create enough chance, we didn't play forward enough and we did not get in behind them and get crosses in enough.
"We've got plenty of time to get that back and try to react on Tuesday."
Seventh placed Peterborough United were beaten at Bradford City, meaning they failed to overhaul Rovers in sixth place.
But that does not concern McCann, who has set his side a tally of wins they must achieve to remain in the top six come the end of the season.
He said: "We're not worried about anyone else, we're worried about ourselves.
"We have to get our form back and we have to start winning games now.
"There are 11 games to go and we need six or seven wins or more than that."