Perez’s late shunt at the Variante Alta led to a last-gasp scramble for drivers to set final qualifying simulation times, where only Lando Norris was able to set a time that put him second, 0.3s slower than his team-mate.
A host of drivers failed to set a time in this late scramble, including Max Verstappen, who now heads into qualifying without a proper sighter on the soft tyres, as he and Perez spent the early part of the session concentrating on their overnight set-up work on the medium tyres.
Ferrari duo Carlos Sainz and Charles Leclerc finished third and fourth with the times they had set during a series of soft-tyre runs in the first third of the session.
Leclerc did attempt to set a late final flying time as he overtook several cars including Sainz with an aggressive outlap as the clock ticked down.
But having got by Piastri and Alpine’s Pierre Gasly on the run to start his last lap, Leclerc’s opening sector was slower than his personal best and he backed off.
Piastri’s session-setting time – a 1m15.529s – came as the pack were preparing more typically for late fliers in the final 10 minutes, but Perez’s accident cut these efforts short and meant even if drivers had had more time to run properly again they were all set to do so on used rubber, including Norris at the head of the pack.
Perez lost his Red Bull’s rear as he bounced down to earth having whacked the kerbs at the Variante Alta’s first apex and his correction sent him off into the gravel and the barriers.
His medium-tyre personal best meant he was shuffled down to 12th by those that did have time to improve pre-red-flag-one, which included George Russell nipping into fifth ahead of Verstappen in a session where both Mercedes cars complained of different ride problems.
The other stoppage came as the halfway stage approach when Alonso (18th in the final order) lost control of the rear of his car turning in from the kerbs between the Rivazza turns and spun off backwards into the barriers on the outside of the final corner.
Fernando Alonso, Aston Martin AMR24, strays into the gravel
Photo by: Zak Mauger / Motorsport Images
Emilia-Romagna Grand Prix – Free Practice 3