Charles Leclerc could not understand Ferrari's strategy during the Monaco Grand Prix, as he lost ground on Formula One leader Max Verstappen.
Leclerc finished fourth in his home race on Sunday after an eventful, rain-soaked grand prix.
Ferrari had closed out the front of the grid and seemed all set to go on and claim a big win, but Red Bull's Sergio Perez clinched victory.
Carlos Sainz finished second ahead of Verstappen to restore some pride for Ferrari, but the Dutchman's lead in the driver's standings grew to four points over Leclerc.
Some strange tactical decisions cost Ferrari, who delayed putting Leclerc on intermediate tyres before then accidentally instructing the Monegasque driver to come in and change to slicks.
Before Ferrari realised their error, Leclerc had already entered the pit lane, allowing Verstappen to overtake him and hold on for a place on the podium.
"Let down is not the word," Leclerc told reporters.
"Sometimes mistakes can happen – but there have been too many mistakes.
"I'm used to getting back home disappointed but we cannot do that, especially in a moment now where we are extremely strong.
"We need to take opportunities. I love my team. We will come back stronger, but it hurts a lot.
"We cannot afford to lose so many points like this. It's not even from first to second, it's from first to fourth because after the first mistakes we've done another one.
"I don't understand what made us change our minds. We got undercut and then stuck behind Carlos [Sainz]. There were a lot of mistakes and we cannot afford to do that.
"The first [radio message for the first pit stop] was a clear decision and a very wrong one. From that moment onwards, the mess started.
"I don't know if it was panic – I don't hear all the background stuff between the team so it's not up to me to judge.
"The last message I had was not clear because I was told to come in and then to stay out but I was already in the pit lane and that's when I let it out on the radio and screamed because I knew it was done."