The 29-year-old lapped the 5.4-km Sakhir desert track in 01:30.824 seconds, 0.141 ahead of Aston Martin’s Fernando Alonso with Red Bull's reigning champion and race favourite Max Verstappen 0.238 seconds off the pace in third.
The Dutchman, his Mexican team-mate Sergio Perez, Alonso and Mercedes racer Lewis Hamilton all took turns at the top before Sainz pumped in his final flying lap.
Charles Leclerc in the other Ferrari was fourth ahead of McLaren’s Lando Norris and George Russell in the Mercedes. Australian Oscar Piastri ended the session seventh in front of Perez, Haas driver Nico Hulkenberg and Aston Martin’s Lance Stroll, who rounded out the top 10. The top 14 drivers were covered by less than a second.
The Friday practice timesheets allayed fears of a predicted Verstappen and Red Bull walkover and raised hopes of a multi-team battle for pole, especially after RB’s Daniel Ricciardo set the pace in Thursday’s opening practice. Hamilton led George Russell in a one-two in the second session.
The Bahrain Grand Prix marks the start of a record 24-race season for Formula One.
The race and the following round at Jeddah in Saudi Arabia a week later are being held on a Saturday to allow the Middle Eastern kingdoms to host races before the start of Ramadan.
