Ferrari chairman Sergio Marchionne believes the Scuderia underestimated Monza and is urging the team to investigate why it's deficit to Mercedes was so important.
Sebastian Vettel salvaged a third-place spot on the podium on Sunday but was never in contention for a race win in the Italian Grand Prix.
"I think we just screwed up," Marchionne told German broadcaster RTL.
"The set-up for the car was wrong. I think we underestimated the circuit. I think we screwed up from Belgium, from Spa, into here.
"If I look at the difference between Mercedes and Ferrari, it's embarrassing. But our goal has not changed. What the Tifosi saw today was simply not the real Ferrari.
"For the first time this season we were below expectations in the race, so obviously we have work to do. But while Monza is Monza, the world championship is still long.
"But the others were almost one second ahead of us, and that's impossible. That is not Ferrari.
"Something has gone wrong. Now, we need to go back to the factory and find out which way the car went sideways. But we will be back in Singapore."
Mercedes' Lewis Hamilton achieved F1's first back-to-back win this season and also took the lead in the world championship for the first time this year.
As predicted, Mercedes successfully negotiated the power-hungry venues which are Spa and Monza, but the Silver Arrows outfit could find it difficult to hold its own at Singapore, a track with a configuration which could play into the hands of the Scuderia.
Gallery: The beautiful wives and girlfriends of F1
Keep up to date with all the F1 news via Facebook and Twitter
