Valtteri Bottas and Lewis Hamilton dominated Qatar Grand Prix third practice with Red Bull's championship leader Max Verstappen off the pace ahead of qualifying later Saturday.
Bottas topped the time sheets with a 1min 22.310, a record fastest lap at the Losail circuit's inaugural Formula One weekend.
Hamilton, who goes into this third last race of the season 14 points behind his arch rival, took second at 0.078sec.
Verstappen appears to have work to do to trouble the Mercedes men as he took third but some 0.341sec off Bottas's effort.
Qualifying for the 20th race of 2021 gets underway under floodlights at 17h00 (1400GMT) with Bottas bidding for his third pole in as many weekends.
The Finn, who moves to Alfa Romeo next season, fronted the grid in Mexico and Brazil, but was overtaken around the first corner in both races by Verstappen.
The Dutch driver duly won in Mexico, but was swept aside by a Hamilton on fire in Sao Paulo last Sunday.
Qatar Grand Prix third practice times
Valtteri Bottas (FIN/Mercedes) 1min 22.310sec (17 laps),
Lewis Hamilton (GBR/Mercedes) 1:22.388 (16),
Max Verstappen (NED/Red Bull-Honda) 1:22.651 (10),
Pierre Gasly (FRA/AlphaTauri-Honda) 1:22.835 (17),
Sergio Perez (MEX/Red Bull-Honda) 1:22.846 (14),
Carlos Sainz Jr (ESP/Ferrari) 1:23.048 (17),
Fernando Alonso (ESP/Alpine-Renault) 1:23.186 (13),
Esteban Ocon (FRA/Alpine-Renault) 1:23.209 (18),
Charles Leclerc (MON/Ferrari) 1:23.276 (17),
Yuki Tsunoda (JPN/AlphaTauri-Honda) 1:23.567 (20),
Daniel Ricciardo (AUS/McLaren-Mercedes) 1:23.711 (14),
Sebastian Vettel (GER/Aston Martin-Mercedes) 1:23.884 (17),
Lando Norris (GBR/McLaren-Mercedes) 1:23.895 (16),
George Russell (GBR/Williams-Mercedes) 1:23.923 (17),
Lance Stroll (CAN/Aston Martin-Mercedes) 1:24.154 (17),
Kimi Raikkonen (FIN/Alfa Romeo Racing-Ferrari) 1:24.246 (19),
Antonio Giovinazzi (ITA/Alfa Romeo Racing-Ferrari) 1:24.288 (17),
Nicholas Latifi (CAN/Williams-Mercedes) 1:24.499 (15),
Mick Schumacher (GER/Haas-Ferrari) 1:24.680 (20),
Nikita Mazepin (RUS/Haas-Ferrari) no time recorded (1)