Benzema had a first-half goal disallowed for offside at the Bernabeu but was otherwise subdued, with the home side failing to register a single shot on target.
The 35-year-old has endured an injury-hit season, featuring in 14 of Madrid's 23 LaLiga games and scoring 11 goals, although he found the net twice in their 5-2 Champions League round-of-16 win against Liverpool at Anfield last week.
"You can't score in every game," Ancelotti said in a news conference on Saturday when asked about Benzema's form. "Karim doesn't worry me. He looks good. He's better than in the first half of the season, for sure. We're fine in attack, we're the team that has scored most goals in LaLiga."
ESPN reported on Friday that Madrid executives were disappointed by Ancelotti's tactics in the Clasico loss, questioning the team's lack of a back up plan as well as the coach's decision to start veterans Luka Modric and Toni Kroos together in midfield.
"I don't think [Kroos and Modric can't play together]," Ancelotti said. "I don't see that problem. The speed of the play isn't about running more, it's about thinking early. Both of them have the experience and knowledge to think before they receive the ball. The ball has to do the running, the ball doesn't sweat."
Ancelotti insisted that Madrid had performed well against Barca, backing them to turn the tie around in the return leg at Camp Nou on April 5.
"I've watched it [again]," he said. "I'll repeat what I've said. It was a good game -- with things to improve -- but a good game."
Madrid travel to Real Betis on Sunday, with the team currently seven points behind Barca in the LaLiga table.