The Spanish giants have scored an impressive 30 goals in their 12 Liga fixtures this season, but the team's frailities at the back have been exposed with the defence being breached on 16 occasions.
Their inconsistency was once again highlighted in Saturday's 3-2 victory over Rayo Vallecano. Having cruised to a 3-0 lead, the hosts stormed back with two quickfire penalties to ensure a nervy ending.
And Ancelotti is keen for his charges to strike a better "balance" in their play ahead of Tuesday's UEFA Champions League meeting with Juventus.
"Balance means to attack and defend well," he said. "We have attacked well but we have conceded a lot of goals.
"I'm not happy with the defensive play but this team has scored an average of about three goals per game."
Ancelotti has opted to rotate his defensive options this season, with Raphael Varane set to come into the starting XI for the trip to Juventus Stadium
And the Italian believes the changes benefit the squad in the long term.
He added: "Varane will play tomorrow (Tuesday), he is fresh because he didn't play on Saturday. I haven't decided who will play with him, (Sergio) Ramos or Pepe.
"The rotations are not a problem, it means the players avoid injury and they are more motivated."
Real will secure qualification from Group B with victory in Turin, but Ancelotti is wary of a tough challenge and praised the work of counterpart Antonio Conte.
"It will be an interesting match," he continued. "For Juventus the game is important, but for us it's an opportunity to qualify.
"Conte has done an amazing job in a difficult environment, building a competitive team."
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