Mercedes is hoping that it will be able to benefit from its strong race pace on Sundays at this weekend's Italian Grand Prix.
However, Leclerc found himself under pressure towards the end of the race as Lewis Hamilton closed in, as the Mercedes driver was more comfortable on the medium compound.
Monza, a high-speed circuit, is set to favour the Ferrari package who has held the advantage in a straight-line over Mercedes this season.
"From a performance perspective, our weekend in Spa gave us plenty to work on," said team boss Toto Wolff. "We were out-qualified and, while our race pace looked promising, we didn't manage to take the win.
"However, given our performance in Belgium last year, it felt like we had also made a step forward. We don't have the fastest car in a straight line this year but we made some progress with regards to the slow-speed corners and the way our car handles the tyres. So there are positives to take away from Spa as well.
"We don't expect the Italian Grand Prix to be an easy weekend. Monza is 'the' power circuit in F1, that rewards high power and low drag.
"While we have had the fastest overall package on the grid this season, it's not ideal for a track where straight-line speed is a key performance differentiator.
"However, we've also seen that the Ferraris look mighty at high-speed tracks on Saturdays, but don't look quite as strong on Sundays - and that's when the points are won. We will not be favourites in Italy, but we will do everything we can to take the fight to the red team this weekend."
With eight rounds left to run in the 2019 world championship, Mercedes holds a 145 gap over Ferrari in the constructors' standings
Bahrain International Circuit - Winter testing