Lewis Hamilton, on the occasion of his first race for Ferrari in Italy, was 11th fastest in the second Ferrari after being fifth, and just 0.096secs from Piastri, in the first session.
The seven-time champion said he had been happy with the car early on but between the sessions he “changed two tiny things that shouldn’t have had any effect at all, the smallest change we’ve probably done this year and we had some brake issues that made a massive difference, so that was then a fight with that.”
Hamilton was vague on what specifically the problem was.
Asked whether it was to do with the change to a different brake manufacturer at Ferrari from the one he was used to with Mercedes for 12 years, he said: “It’s not the transition. It’s the performance of…” and then his voice trailed off.
In the pool interview, which is the only driver access provided to the media on Friday, he was not pressed for an explanation.
He added: “It’s a lottery. We will roll the dice. We put on one and it works, put another one on and it doesn’t and we’ll see. I hope tomorrow we figure something out. We’re working on it for sure.”
Russell, who has had strong qualifying form this season, said that the decision to bring the softest three tyre compounds to this race could have an influence.
Pirelli has widened its range to six compounds this season, introducing a softest tyre that was originally intended only for street circuits, where tyre degradation is usually low.
However, it has been decided to use it in Imola to try to add an extra dimension to the grand prix, hoping the softer range of compounds might shift the race away from from the standard one-stop strategy at the track.
Russell said: “There is a lot of tyre degradation. We have the softest tyres here for the first time this season and that spices things up a bit.
“But we know McLaren generally seem to extend their advantage in those conditions.
“I had Oscar in my sights and then I didn’t. He passed Max and then went off. That’s just where we are at the minute as a team. We know our fight is with Max and the Ferraris.”
Williams driver Alex Albon said he did not expect strategy to change, saying the medium tyre had proved “really good” with “pretty low deg”.
The race runs were interrupted when Isack Hadjar, seventh fastest overall for Racing Bulls, lost his car on the exit of the Tamburello chicane and spun into the barriers.
The car appeared to have escaped largely undamaged, but Hadjar became stuck in the gravel as he attempted to return to the track and the session was red-flagged.
It did restart, but only in time for some drivers to do a single flying lap.
Behind Hadjar in the list of fastest times, Yuki Tsunoda was eighth fastest in the second Red Bull, ahead of Albon and team-mate Carlos Sainz.
Lance Stroll, given the responsibility to test Aston Martin’s major upgrades, which included a new floor, was down in 17th.
Team-mate Fernando Alonso, in the previous-specification car for a back-to-back comparison, was three places higher and 0.121secs quicker.
Stroll said the car felt “the same”. And although it features a new floor and engine cover, the Canadian described the upgrade as “small changes”.
The first practice session had been brought to a premature end when Sauber’s Gabriel Bortoleto crashed at the second Rivazza corner, flicking into the barriers pretty much front-on and damaging his front wing and nose.
