Despite the fact there were no Mercedes cars within the top two, both Silver Arrows of Lewis Hamilton and Valtteri were third and fourth respectively on the hard tyres, compared to the softs that were used by Verstappen and Vettel.
Bottas' session ended early as he crashed into Turn 19 after losing the rear when turning in. The Finn also tapped the wall at the same corner earlier in the session, damaging a wheel rim.
A red flag was deployed while the stricken W10 was recovered by the marshalls, with Bottas stating on his way back to the Mercedes garage that the accident was "my bad".
The second Red Bull of Alexander Albon was fifth fastest, 1.2 seconds down on his teammate, who set the pace for the session.
Charles Leclerc also missed out on a lot of running, as a gearbox issue halted his programme. Ferrari confirmed it is investigating the cause of the problem.
Two-tenths behind Sainz in eighth was the second McLaren of Lando Norris, who ran wide at Turn 9 during the session, opting not to take the corner after detecting a minor instability issue.
Bahrain International Circuit - Winter testing