George Russell topped the times for Mercedes after Charles Leclerc crashed his Ferrari during Friday's second practice at the Mexico Formula One Grand Prix.
Russell offered a hint of Mercedes' potential with a strong performance in a session devoted to tyre testing, in changeable conditions, while Leclerc, unhurt, was left to watch from the Ferrari garage.
The 24-year-old Briton took advantage of a chance to shine as one of only a few drivers permitted to run on 2022 tyres and clocked a best lap in one minute and 19.970 seconds on softs.
This lifted him eight-tenths of a second clear of Yuki Tsunoda in his Alpha Tauri and Esteban Ocon of Alpine, both also allowed to use half the session to work on set-up with regular tyres after handing their cars to guest rookies for the opening practice.
Russell's Mercedes teammate, seven-time champion Lewis Hamilton, was fourth-quickest in a session interrupted by two red flags.
The first came when Leclerc spun off heavily in his Ferrari and a second in the closing minutes when Zhou Guanyu suffered a hydraulic failure in his Alfa Romeo.
That brought the session to an early end and left Ferrari frustrated after dominating the opening practice when Carlos Sainz topped the times.
Two-time world champion Max Verstappen was sixth, one place behind Red Bull teammate Sergio Perez, who was given enthusiastic support by his home fans.
Leclerc wound up seventh ahead of Sainz, Alfa Romeo's Valtteri Bottas and Pierre Gasly of Alpha Tauri.
After a morning filled with political debate following the announcement by the FIA of Red Bull's punishment for last year's cost-cap breach and Ferrari's dominance of opening practice, there was an air of welcome calm as the second session began.
In warm but overcast conditions with rain threatening, the 90 minutes were cast to be used as an extensive Pirelli tyre test, concentrating on a range of soft compounds for consideration next year.
This gave the action an air of pre-season testing rather than race preparation, although those drivers who took no part in the earlier session, having given their cars to rookie reserve drivers, were permitted to use half of the session for set-up work this year’s tyres.
The 2023 tyres were all unmarked and unpredictable.
Russell and Ocon were swiftly involved in the action and Perez provided his adoring fans with a reason to cheer on every passing lap, but there was little urgency before Sainz went top for Ferrari.
He was followed by Russell, on mediums, before Verstappen with a set of tester softs and then Perez set the pace until Russell, in 1:19.970, went 1.6 seconds clear after 20 minutes on fresh soft tyres.
Leclerc then crashed, after 33 minutes, spinning backwards into the barriers at turn seven and badly damaging the rear of his Ferrari to prompt a red flag stoppage that lasted 20 minutes.
He was unhurt, but it was a setback to him and the Ferrari team at a venue where they have not won since Alain Prost triumphed in 1990.
As the sky darkened, the track conditions deteriorated. The falling temperatures offered less grip as the cars slithered around ensuring Russell's lap remained the fastest.