The Monza pole-sitter punched in a 1m32.120s to top the session amid the soft-tyre phase of running, which withstood a siege from Leclerc despite Sainz’s inferior first and second sectors.
Being set at the same time of day as qualifying and the race, FP2 was considered the sole representative practice session as the track had cooled under the night sky.
Leclerc set the pace on the medium compound with his final run on the yellow-walled tyres, overturning team-mate Sainz’s advantage at the top by approximately a quarter of a second as the Spaniard had largely bossed the top of the timing boards in the early phases of the session.
Sainz had previously eclipsed brief headliner Fernando Alonso with a 1m33.303s, which he’d brought down to a 1m33.213s on his next flying run, but Leclerc was the first below the 1m33s bracket with his 1m32.974s.
This preceded a small break in running before the field returned to the circuit on the soft compound to simulate their qualifying runs as track conditions cooled further.
Sainz was ahead of Leclerc on the road and had to endure his opening pair of sectors being narrowly shaded by the Monegasque by a whisker, but set the benchmark of a 1m32.120s regardless.
Leclerc then suffered a snap at Turns 18 and 19 and rattled over the kerb moments before crossing the start-finish line, which cost him the small margin he’d built and left him to fall short by 0.018s.
The Ferraris took a second lap on the softs, but neither driver improved and their times remained at the top of the timing boards for the rest of the session.
George Russell got closest to them having been 0.235s off the pace, despite a few wayward moments at the wheel of his Mercedes W14. His effort chiselled Alonso out of the top three as the two-time champion had to be content with fourth in the overall order.
Four-time Singapore Grand Prix winner Lewis Hamilton was fifth fastest over McLaren’s Lando Norris, who was fully equipped with the Woking squad’s latest package of upgrades.
In the meantime, the Red Bulls were unable to find any meaningful front-running pace and struggled particularly with a wayward rear. On one of his early runs on the medium tyre, Verstappen couldn’t get his RB19 to bite into the Turn 13 apex and then skated wide on the exit as he lit up the rears.
Team-mate Sergio Perez also struggled with a nervous car and complained that “in every braking zone, I feel like I’m going to crash”, but nonetheless outpaced his championship-leading team-mate.
Nordic duo Kevin Magnussen and Valtteri Bottas completed the top 10, the Finn functioning as the meat in a Haas sandwich as Nico Hulkenberg assumed 11th overall.
Alex Albon propped up the order having set his fastest lap on the hard tyre, as a power unit issue ensured that the London-born Thai could not set a representative qualifying simulation on softs.