Valtteri Bottas set the fastest time in Practice Three for the Azerbaijan GP as Sebastian Vettel and Max Verstappen suffered mechanical problems.
Bottas posted a 1:42.742 to top the timesheets by a tenth of a second from Kimi Raikkonen, with Mercedes team-mate Lewis Hamilton in third.
But Hamilton's championship rival Vettel saw his track time severely limited by a water system issue and only managed the 12th-fastest time.
And Friday's pace-setter Max Verstappen saw his session come to a premature end when his car stopped on track, the Dutchman having earlier complained of an engine issue.
Jolyon Palmer was also restricted to just six minutes of running after his Renault engine caught fire and it remains to be seen if he will be able to take part in qualifying.
Daniel Ricciardo was fourth fastest, half a second down on Bottas, while Esteban Ocon displayed Force India's impressive pace to end the session fifth.
"It's all to play for in qualifying," Sky F1's Damon Hill said.
Both Williams cars finished within the top 10 with Daniil Kvyat and Sergio Perez completing the front runners.
The McLarens of Fernando Alonso and Stoffel Vandoorne were 14th and 16th respectively, with both drivers facing hefty grid penalties for engine component changes.
Azerbaijan GP Practice Three Timesheet
1. Valtteri Bottas, Mercedes, 1:42.742
2. Kimi Raikkonen, Ferrari, +0.095
3. Lewis Hamilton, Mercedes, +0.416
4. Daniel Ricciardo, Red Bull, +0.545
5. Esteban Ocon, Force India, +0.602
6. Max Verstappen, Red Bull, +0.872
7. Felipe Massa, Williams, +0.996
8. Daniil Kvyat, Toro Rosso, +1.166
9. Lance Stroll, Williams, +1.298
10. Sergio Perez, Force India, +1.396
11. Nico Hulkenberg, Renault, +1.570
12. Sebastian Vettel, Ferrari, +1.602
13. Carlos Sainz, Toro Rosso, +1.659
14. Fernando Alonso, McLaren, +1.999
15. Kevin Magnussen, Haas, +2.184
16. Stoffel Vandoorne, McLaren, +2.401
17. Romain Grosjean, Haas, +2.749
18. Marcus Ericsson, Sauber, +2.903
19. Pasccal Wehrlein, Sauber, +2.980
20. Jolyon Palmer, Renault, +10.268
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