Ferrari team principal Maurizio Arrivabene believes Mercedes' overconfidence cost Lewis Hamilton victory at the Monaco Grand Prix.
Hamilton had a 24s lead over team-mate Nico Rosberg and Ferrari's Sebastian Vettel when the Safety Car was deployed with 15 laps still to go.
Those on the Merc pit wall decided to pit their leading driver for fresher rubber as a precautionary measure, but Rosberg and Vettel opted to stay out and Hamilton ended up finishing third.
Asked if they considered pitting Vettel, Arrivabene replied: "No, actually it was the opposite and we were nervous at the beginning thinking about them to pit. We were looking for the window and our strategist said: 'We stay cool, they are doing a kind of show'.
"In any case, he said that if they come in then we would stay out. He was really straightforward on this and he was right. I know that we were lucky [to get second], I'm not telling you something different.
"[But] in my opinion, they were a bit too much convinced about their power. I recognise they are very intelligent and stronger than us, but this time we were smarter."