Kevin Magnussen took advantage of Haas' extra hour of running late on Friday to set a surprise fastest time on the penultimate day of pre-season testing, after Carlos Sainz had earlier set the pace for Ferrari in Bahrain.
The official end of the day came at 7pm local time in Bahrain, although Haas were granted an extra hour of running after they missed the opening Thursday morning session due to travel delays.
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And in that hour, Magnussen - marking his return to Formula 1 in style - recorded a lap of 1:33.207 to go 0.3 seconds faster than Sainz, with cooler track conditions likely a factor in the significant improvement to what Haas have shown so far in pre-season.
World champion Max Verstappen was third for Red Bull with Lewis Hamilton fifth for Mercedes, with the pair separated by Lance Stroll, who produced an encouraging display for Aston Martin.
While Sainz himself warned on Friday that Mercedes could be holding back performance for next weekend's season-opener at the same circuit, Ferrari enjoyed another impressive day to maintain the form they have shown since Formula 1's all-new cars were first revealed in Barcelona.
Sainz's time of 1:33.532 was nearly half a second quicker than Pierre Gasly's pace-setter for AlphaTauri on day one, and a similar margin ahead of his closest challenger Verstappen on Friday.
Despite Lando Norris finishing eighth, McLaren's track time was severely limited for a second successive day by an issue with their brakes, which has left them awaiting the delivery of revised parts from the team's UK factory.
A dramatic fire on Nicholas Latifi's car saw Williams complete just 12 laps, while Alfa Romeo were hampered again by technical issues.
Esteban Ocon finished sixth after topping the morning timesheet for Alpine, who appeared to enjoy an improved day of performance despite the Frenchman later forcing a red flag with a "precautionary" stop on track.
Hamilton tips Ferrari as favourites
Ferrari have been a near-constant presence near the top of the timesheets - and equally importantly - on the track throughout the pre-season.
Friday was no different as Charles Leclerc was second to Ocon in the morning as he completed 54 laps in a session most teams appeared to use to focus more on longer runs. Sainz then took over, completing 60 laps in the afternoon as he knocked Ocon off top spot before further improving his time.
Ferrari are looking to bounce back after being totally outperformed by Mercedes and Red Bull last season, and many in the paddock are starting to believe the Italian team could be highly competitive to start the new campaign.
"That was a very satisfactory day for Ferrari," Sky Sports F1's Martin Brundle said. "Good speed, good consistency, good reliability."
Hamilton added, with the Bahrain GP just over a week away: "From what I can see, today Ferrari would probably be getting a one-two."
The Mercedes, which dominated the headlines on Day One in Bahrain with its radical 'no sidepod' design, appeared tough to handle once more on Friday, as George Russell then Hamilton both struggled at times.
Hamilton's best time came on a softer - and theoretically faster - tyre than the one used by Sainz and Verstappen, suggesting he may have been further back from the top two than it appeared.
However, it was not until the final stages of last month's shakedown in Barcelona that Hamilton set the fastest time of the week, and speculation remains rife that the Silver Arrows are holding back a significant amount of performance.
Speaking between Friday's sessions, Red Bull principal Christian Horner admitted only time will tell how quick the Mercedes is, but said the Ferrari is the car that looks "most settled".
Red Bull themselves have rarely threatened the top of the timesheets during the pre-season, but on Friday afternoon Verstappen finally displayed some speed to move within half a second of Sainz.
Magnussen's stunning return
Haas' extra-time showing came as somewhat of a shock after an exhaust issue limited Mick Schumacher to just 23 laps in the morning session, which largely characterised how their pre-season had gone until that point.
Magnussen, making his return to the team following the dismissal of Russian driver Nikita Mazepin, took little time to readjust to F1 after two years out of the sport.
The Dane took advantage of having the track to himself in cooling conditions to set a time that will undoubtedly raise great intrigue along the pit lane.
Haas have been granted four hours of extra running in total, with Magnussen to complete an hour during Saturday's lunch break, and Schumacher two hours following the final day's chequered flag.
Norris, shouldering McLaren's driving responsibilities alone for a second successive day in the absence of the unwell Daniel Ricciardo, completed just 60 laps, with the team admitting the brake issue had forced them to cap stints on track at a maximum of 10 circuits.
Principal Andreas Seidl revealed that revised brake ducts were being manufactured at the team's Woking factory, with the hope they could arrive in time to be used on Saturday's testing finale.
Perhaps the most dramatic moment of the day came in the morning session as the brakes on Latifi's Williams caught fire, with some parts on the back of the car exploding as a marshal attempted to extinguish the flames.
The team would later confirm that the fire was caused by a "minor" issue and that their withdrawal from the remainder of the day was a result of other damage caused by the fire.
A hydraulics issue on Valtteri Bottas' Alfa Romeo brought out a red flag to end the morning session as the Finn completed just 25 laps, but Chinese rookie Zhou Guanyu was able to manage some significant running in the afternoon.
Elsewhere, there were solid days for Aston Martin and AlphaTauri, who both comfortably completed in excess of 100 laps