Valtteri Bottas made it a clean sweep earlier, the Finn topping the timesheets in all three practice seconds.
However, the hot breath the Mercedes driver could feel down the back of his neck wasn't from his teammate, but Max Verstappen who was just 0.017s behind.
Strong on the mediums and the softs, the Dutchman looks set to take the fight all the way to the Black Arrows this afternoon and tomorrow.
Naturally, we're not writing-off Lewis Hamilton, who was only 0.083s off Bottas' pace, we're simply making clear that Master Max is very, very much in the mix.
Behind these three it's pretty much up for grabs, with Racing Point and AlphaTauri looking strong, while Renault and McLaren have yet to find their feet.
Despite this weekend being a celebration of Ferrari's longevity - tomorrow's race being the Maranello squad's 1,000th Formula One World Championship start - it's unlikely the Italian team will have much to cheer about, Messrs Leclerc and Vettel lucky to finish in the points... never mind on the podium.
Kimi Raikkonen, who made his F1 (test) debut here twenty years ago (yesterday) has looked strong all weekend, and surely nobody would deny the 2007 world champion a few points tomorrow.
If there are any positives from the pandemic, F1's log-awaited arrival at Mugello has to be one of them, the Tuscan dream everything we all expected... and more. And with the likes of Portimao, Istanbul and Imola still to come, it's hard to believe the phoenix that has risen from the flames of Melbourne all those months ago.
Ahead of Q1, the air temperature is 29 degrees C, while the track temperature is 46 degrees. It remains bright and sunny.
In a late move, while officials have allowed the gravel traps to decide the track limits, a directive has been issued notifying that drivers who cut the chicane (Turns 13/14) will have their times deleted.
The lights go green and first out is Russell who failed to post a time earlier today due to a brake-by-wire issue. The Williams driver is joined by his teammate.
Russell posts an 18.024, with Latifi posting 17.924 moments later.
Stroll and the Alfas - a good name for a band - head out. As do the Black Arrows and Verstappen.
Stroll goes quickest with a 16.701, ahead of Giovinazzi, and Raikkonen, only for the Alfas to be demoted when Perez posts 17.008.
Norris can only manage fifth (17.350), as McLaren continues to struggle.
Wham, bam, thank you... Hamilton posts 15.778 only for Bottas to respond with a 15.749.
Verstappen can only manage 16.335, 0.586s off Bottas' best.
Vettel goes tenth (17.343), with Leclerc posting 17.048 to go seventh moments later.
Albon goes sixth with a 17.018, while Ricciardo goes tenth and his Renault teammate eleventh.
Racing Point is running new bargeboards this weekend, but as it only has one set it is Latifi who gets them... because he is ahead of Perez in the championship.
A 17.320 sees Latifi go 13th.
With 5:50 remaining, the drop zone comprises Gasly, Raikkonen, Russell, Grosjean and Magnussen, with Norris, Vettel and Latifi hovering.
Behind the leading three, the rest of the field is covered by under a second.
One by one they head out for the final assault, though it is unlikely we will see the Mercedes pair or Verstappen.
That said, Hamilton heads down the pitlane.
Perez, who went out much earlier than anyone else, improves from fifth to fourth with a 16.596. Teammate Stroll has settled for his time.
Lots of PBs in the opening sector, though Russell messes up his second.
The Briton goes 12th, while Magnussen goes 16th.
Ocon goes 6th and Raikkonen 9th.
Grosjean goes tenth as the times tumble. All except for Gasly who can only manage 14th.
Sainz goes 8th, but is quickly demoted by Ricciardo and then Norris.
Leclerc goes sixth and Vettel 15th, the German once again making the cut by the skin of his teeth.
It's back to reality for Gasly, who misses the cut, along with Giovinazzi, Russell, Latifi and Magnussen.
Quickest is Bottas, ahead of Hamilton, Verstappen, Albon, Perez, Leclerc, Stroll, Ocon, Norris and Kvyat.
Replay shows Vettel having a big moment at Turn 4 as the wind picks up.
Unusually, when the lights go green, there are a number of drivers ready and waiting at the end of the pitlane, with Hamilton and Bottas heading queue.
As more and more drivers head out, all are sporting the softs, nobody seemingly willing to gamble on the mediums.
Hamilton has the edge in S1, and again in S2. At the line the Briton posts 15.309, while Bottas can only manage 15.322 and Verstappen 15.471.
Stroll goes fourth (16.271), ahead of Leclerc, Ocon and Perez, only to be demoted when Albon goes fourth (15.914) and Ricciardo fifth (16.243).
Norris is tenth, ahead of Kvyat, Sainz, Vettel, Raikkonen and Grosjean.
A breathless Ricciardo admits that "that one was pretty decent".
Replay shows a highly questionable release for Stroll, right into the path of Verstappen. The Dutchman takes it in his stride... not even the mildest of profanities crossing his lips.
The Points are first out, followed by the Ferrari, shades of Monza as teammates are clearly seeking a tow.
Perez posts a PB in S1, as does teammate Stroll. The Mexican crosses the line at 16.489 to go ninth, while Stroll fails to improve and remains sixth.
Vettel improves his time but remains 13th, once again he misses the cut. Raikkonen improves to 13th.
Sainz improves to tenth, thereby demoting his teammate, while a poor second sector sees Kvyat fail to improve.
Raikkonen improves to 13th, he misses the cut but finishes ahead of Vettel. Leclerc is 8th.
Quickest is Hamilton, ahead of Bottas, Verstappen, Albon, Ricciardo, Stroll, Ocon, Leclerc, Perez and Sainz.
We lose Norris, Kvyat, Raikkonen, Vettel and Grosjean. Raikkonen and Kvyat posting exactly the same time.
Check out our Saturday gallery from Mugello, here.