A controversial goal from former Rovers player Stephen Warnock - after defender Ryan Nelsen looked to have been fouled by Villa striker Gabriel Agbonlahor - handed the home side a lifeline.
Allardyce, who steered Bolton to victory over Villa at the semi-final stage six years ago, is glad Rovers have a blank weekend ahead as they try to regroup for the task of staying in the top flight.
But he also claims Blackburn should survive comfortably if they demonstrate the same quality evident against Villa.
He said: "We've got to get over this setback. We were unfortunate, we had decisions go against us, but we can take a lot of heart from our performance.
"Can we build on that in the Premier League? I don't know. I don't know what the legacy of what's happened to us (against Villa) will be.
"I am damned glad we haven't got a game on Saturday.
"I've got some totally and utterly dejected players and I've got to make sure they overcome this bitter disappointment and get on professionally with what we've got to do now.
"That is to look at the Premier League and work our way up as far as we can and for me to say to them, 'Continue to play like that lads and we won't have a problem and we can enjoy working our way up the league'.
"We can't let this be a hangover going into the Premier League games because we can ill afford that."
Allardyce accepts there is room for improvement in certain areas of his side and some of the defending left a lot to be desired against Martin O'Neill's side.
He said: "There are obviously some areas we can blame ourselves for - some of the goals we gave away.
"But, at critical times of the game, if a decision goes against you, it makes a massive difference."
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