Max Verstappen topped the times for Red Bull and delivered a reality check for Mercedes new boy George Russell in Saturday's third and final free practice for Sunday's Sakhir Grand Prix.
The Dutchman delivered a best lap of 54.064 seconds at the fast, short-lap 'outer loop' of the Bahrain International Circuit to finish ahead of Valtteri Bottas of Mercedes and Alpha Tauri's Pierre Gasly.
Russell, released by Williams to replace coronavirus victim and seven-time world champion Lewis Hamilton in the title-winning Mercedes team, was unable to repeat his impressive Friday form, when he topped both sessions.
He wound up seventh behind fourth-placed Esteban Ocon of Renault, Lando Norris of McLaren and Alexander Albon in the second Red Bull after swapping quickest laps with Bottas during the early part of the session.
Sergio Perez was eighth ahead of his Racing Point team-mate Lance Stroll and Ferrari-bound Carlos Sainz of McLaren.
Ferrari duo Charles Leclerc and four-time world champion Sebastian Vettel were 13th and 15th in what turned out to be a very tight and competitive session.
The session began at sunset with an air temperature of 25 degrees and the track at 30, but as night fell so did those numbers as debutant Pietro Fittipaldi, the Brazilian substitute for Romain Grosjean at Haas, ventured out. For 15 minutes, he was the only man on track.
When he pitted, Norris led the rest into action, the McLaren driver going top before being succeeded by Ricciardo, Leclerc and Bottas.
Verstappen spun into Turn Two, but recovered just as Russell, Friday's top man, took over briefly only for his 'black arrows' team-mate to regain the ascendancy with two fastest laps, establishing a 0.477 gap ahead of the young Englishman.
It stayed that way until Vettel, rediscovering some form, jumped to second before the final runs with both Mercedes men switching to shiny new softs.
It was but fleeting encouragement for him, however, as within minutes Ferrari announced he needed a precautionary change of engine for qualifying –- a major task to complete in just two hours.
Bottas, clearly revitalised after a dismal Friday, clocked 54.270.
That flurry of action was followed by Verstappen leaping beyond them all in 54.064 to create an enticing scenario with five different teams taking the top five places and only seven-tenths of a second separating the Dutchman from 15th-placed Vettel.
Much as expected, Fittipaldi wound up 19th ahead only of fellow debutant Jack Aitken, the young Briton standing in for Russell at Williams.