Lewis Hamilton was pipped to the top of the time sheets by his Mercedes team-mate Valtteri Bottas in second practice for the Italian Grand Prix.
Hamilton, who trails Sebastian Vettel by seven points in the championship race, posted the fastest lap on Friday morning as he bids to build on his victory in Belgium last weekend.
But it was Bottas, in the sister Mercedes, who led Hamilton at the so-called Temple of Speed with Vettel in third and his Ferrari team-mate Kimi Raikkonen fourth.
Just as in Spa-Francorchamps a week ago, the high-speed nature of this famous Monza track had been expected to suit Hamilton's Mercedes car.
And so it proved here with Mercedes securing a one-two in both practice sessions, first through Hamilton and then Bottas.
Bottas' best lap of one minute and 21.406 seconds enabled him to finish just five hundredths of a second clear of Hamilton.
Hamilton will surpass Michael Schumacher's all-time record with pole position tomorrow, but the Briton will not only have Bottas to contend with for top spot on the grid.
Ferrari, in front of their home support, appeared off the pace this morning, but they ended the day within striking distance of the Mercedes cars, with Vettel, leading the chase, just 0.140 sec adrift of Bottas.
Behind the Mercedes and Ferrari drivers, Max Verstappen and Daniel Ricciardo finished fifth and sixth, but the Red Bull duo will be thrown towards the back of the grid following engine changes on both cars.
Fernando Alonso is the last driver to win in a Ferrari in front of the passionate Tifosi. But the Spaniard, who triumphed at Monza back in 2010, is also due to start Sunday's race from the back of the field after McLaren's beleaguered partners Honda confirmed he will serve a 35-place drop following further engine penalties.
The 36-year-old, out of contract with McLaren at the end of the year, was eighth in second practice with his team-mate Stoffel Vandoorne one place higher up.
Britain's Jolyon Palmer is one of only two drivers yet to score a point this season, and he was 13th here, one spot, and one tenth of a second behind his Renault team-mate Nico Hulkenberg.
Elsewhere, Esteban Ocon, who has vowed to move on from his embarrassing collision with Force India team-mate Sergio Perez at the last race, finished ninth in the order ahead of Felipe Massa for Williams.