After being a match for Red Bull in the first part of the season, Ferrari has fallen behind the Milton Keynes outfit, and runaway championship leader Max Verstappen in particular, since the summer break.
With Verstappen dominating at high-speed Spa and also winning at Zandvoort, a track which should have suited Ferrari more, Leclerc fears this weekend's Italian Grand Prix could be a repeat of Spa given Monza's focus on top speed.
"I think it's going to be a bit of a difficult weekend, on paper at least it's going to be a difficult weekend," he said in Thursday's pre-event press conference.
"We expect Red Bull to be stronger. The track characteristics don't fit exactly our cars.
"But again, we've had some good and bad surprises this year, so hopefully this one is one of the good ones and that we overperform compared to what we expect."
While Leclerc thought it was "difficult to know" whether Ferrari's straightline deficit is down to a difference in power or aerodynamic efficiency, he thinks whatever advantage Ferrari could eke out in Monza's low to medium speed corners will not be able to compensate for the copious amounts of laptime it is set to lose on the long straights.
"I think comparing to Red Bull especially, because it's a bit more consistent through the whole year, we are slower down the straights," he added.
"Their main strength this year is the straight-line speed. We seem to be a little quicker in the corners, but on tracks like here it's not enough to gain back the advantage that they have on the straights.
"Compared to Red Bull I think this will be the case this weekend. Compared to Mercedes it is difficult to make predictions for this weekend, they have had ups and downs."
