Why Doncaster Rovers will pore over their "worst performance of the season" earlier than scheduled
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Rovers failed to test AFC Wimbledon keeper Alex Bass as they were comfortably beaten 2-0 at the Cherry Red Records Stadium on Saturday.
McCann's side had scored at least twice in ten of their 13 previous fixtures before the weekend and appeared to have turned a corner with their away form.
McCann told The Free Press: "We will go over and analyse it. Usually when we have a three-game week or a busy week we will debrief both games on a Thursday, but this will need to be looked at on Monday.
"We have to learn from what we have done wrong."
Doncaster have a quick turnaround before their next match against Accrington Stanley tomorrow night.
That game will also take place away from home, where Rovers have struggled to produce their best form this term.
McCann lost defender Joseph Olowu to a concussion on Saturday with winger Luke Molyneux subbed at half time after damaging his ribs.
FA rules state players are not allowed to return to playing for at least six days after suffering a concussion, meaning Olowu will not be available for tomorrow's FA Cup first round replay.
On Molyneux, who has been one of the team’s best performers this season, McCann said: "He's either bruised or cracked his ribs.
"He's had it for a while but he picked another knock up with it today (Saturday). He wasn't himself, hopefully he can improve before Tuesday."
The winner of tomorrow night's tie will bank £41,000 in prize money.