The Italian coach was not impressed with his star-studded team's display as he feels that they made too many mistakes and were fortunate to bag the full three points
The Ligue 1 newcomers made it four wins from five matches thanks to Radamel Falcao's sixth-minute penalty at the Stade Louis II but the former Juventus boss lamented the number of mistakes that his side made during the clash.
"I am a little bit angry as we made too many mistakes. We did not pay enough attention on our passing and didn't raise our game," the Italian said at a press conference.
"It was important to have the possession of the ball. We won 1-0 but they did create many chances; it was a tight game."
Ranieri believes that his side made life difficult for themselves during the clash, citing a Falcao chance that was not taken in the second half as a missed opportunity.
"We were in control for most of the game and, in the end, it was more complicated," he continued.
"I am satisfied with the way we played except for some bits during the first half. I think that Falcao had the opportunity to score the second goal."
Monaco face champions Paris Saint-Germain at the Parc des Princes in their next Ligue 1 fixture on Sunday.