Red Bull driver Max Verstappen was the quickest man in the final practice session ahead of qualifying in Bahrain, having pipped Ferrari's Charles Leclerc by less than a tenth of a second.
But, after a tough Friday, Mercedes showed they might be a threat going into the first qualifying session of the season.
With the reigning Constructors' World Champions having struggled for pace throughout the Bahrain test, and the first practice day of the weekend, both George Russell and Lewis Hamilton put in some eye-opening times as the drivers delivered hot laps on the Soft tyre.
Leclerc had initially set the pace, before Verstappen put in a time seven-tenths of a second clear of the Monegasque, with the pair trading fastest laps on the red-marked Pirelli rubber.
Mercedes join in the fight at the front
With just 20 minutes remaining, Hamilton came out on track and, with a visibly less bouncy Mercedes, finished less than a tenth down on his 2021 title rival. Moments later, Russell went faster than everyone, as he logged a 1:32.935 on the Softs, demoting Verstappen down to second.
But Friday pace-setters Verstappen and Leclerc weren't finished. The Ferrari driver popped in a 1:32.640 to go quickest, with Verstappen coming out again for another go on the Soft tyres. The Dutch driver made a mistake into Turn 1 on his first attempt and backed off, but regrouped to set a 1:32.544 to go quickest by 0.096 seconds over Leclerc.
Underlining Red Bull's pace was the late jump from Sergio Perez, after a Friday spent evaluating different set-ups. He clocked a time a quarter of a second down on Verstappen with five minutes remaining, but a tenth-and-a-half quicker than Russell.
Result Free practice 3 - Bahrain
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Haas and Alfa Romeo impress
The Haas and Alfa Romeos proved competitive in the final practice session, with Kevin Magnussen slotting into seventh in the final minutes as he set a time just three-tenths slower than what Hamilton managed in sixth.
After Valtteri Bottas' strong second practice showing on Friday, the Finn impressed again by placing in eighth and just ahead of rookie teammate Guanyu Zhou.
Rounding out the top 10 was Aston Martin's Lance Stroll, 1.376 seconds away from the best time.
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