While the nine-times European champions have had little trouble finding the net this season, largely thanks to the scintillating form of Cristiano Ronaldo, their defence has been fragile and they have only managed three clean sheets in 15 games in La Liga and one in five Champions League outings.
Ramos got himself sent off midway through the first half at the Bernabeu when he allowed Umut Bulut to get in front of him before felling the Galatasaray forward when he was through on goal.
If Real are to claim the 10th European crown that has eluded them since their last success in 2002 they will need to tighten up at the back as their opponents in the knockout round are likely to offer a much stiffer challenge than tame Galatasaray.
"The match was made more difficult by the Sergio Ramos sending off," Ancelotti said in an interview with Spanish television broadcaster Canal Plus.
"I don't think the defenders should be taking risks, all they need to do is cover behind them and nothing more," added the Italian, who was clearly upset with Ramos as the Spain international trudged off the pitch.
"We suffered a sending off because of that and also for the Galatasaray goal when we didn't cover our backs properly.
"I have told the defenders many times that they have to cover behind them and I don't need to say it again."
One bright spot in defence in Wednesday's game was the performance of fullback Alvaro Arbeloa, who scored Real's second goal and set up Angel Di Maria for the third and was named "man of the match" by Ancelotti.
The former Liverpool player's performance earned him a huge ovation from the Real fans and his goal was only the second one he has netted in 56 Champions League appearances.
"I am happy to be back among the goals," Arbeloa joked in a post-match TV interview.
"Thankfully they don't pay me for scoring but it is always important to help the team," added the Spain international.
"I told the president that if (injured) Cristiano was not available I would take care of the goals."
- Sports & Recreation
- Cristiano Ronaldo
- Sergio Ramos
- Didier Drogba
- Umut Bulut
- Iker Casillas