The Ghanaian was forced off 14 minutes to fulltime as the Eagles slumped to a 3-0 home defeat at Selhurst Park.
Raheem Sterling, Leroy Sane and Yaya Toure scored to send the Citizens to the fifth round.
“Only time will tell if that [defeat] is a blessing or not but you want to try and win every game you play, and we’ve lost the habit of winning," Allardyce said.
"Our game is okay in parts and we look quite comfortable, but then we make errors and the first two goals today proved that opposition of Manchester City’s quality will punish you.
"For me it’s still about working to minimize those errors and that if we do make one, then we don’t allow the opposition to score but that was the problem again today.
“Schlupp is a big blow with a hamstring problem so he’ll be missing for a while."
Schlupp joined Palace earlier this month from reigning champions Leicester City on a four-and-a-half-year contract.
Saturday's outing was his third appearance for Allardyce's outfit.