Max Verstappen raised the possibility of a fascinating championship duel with Lewis Hamilton by completing a practice double in Bahrain.
As Formula One roared back into life here in the Gulf Kingdom, Verstappen delivered on Red Bull's encouraging pre-season form to end both of Friday's sessions at the top of the time charts.
Hamilton, who galloped to his record-equalling seventh world title with three rounds to spare last year, was third, 0.235 seconds behind.
Lando Norris split Verstappen and Hamilton finishing second, and within one tenth of the Red Bull driver, on an impressive evening for the British driver and his resurgent McLaren team.
Ferrari's new signing Carlos Sainz was fourth ahead of Mercedes' Valtteri Bottas, with Daniel Ricciardo sixth following his switch from Renault to McLaren.
On the eve of the new campaign Hamilton said his all-conquering Mercedes team was no longer the fastest on the grid.
And judging on the evidence of the opening day of the new campaign, it certainly appears as though Hamilton will not have it all his own way as he bids to move clear of Michael Schumacher with an unprecedented eighth world title.
Mercedes have dominated the sport, winning the past seven drivers' and constructors' championships, but there is now a growing feeling that the chasing pack have managed to close the gap. Indeed, 15 of the 20 drivers were covered by less than one second.
Red Bull have been slow out of the gates in recent years, but Verstappen posted the fastest time of the winter test before going on to finish top of the charts in both outings on Friday.
McLaren finished third in last year’s constructors standings – their best result since Hamilton left the British team at the end of 2012 – and, now powered by Mercedes, they followed up an encouraging pre-season campaign with Norris just 0.095 second adrift of Verstappen.
Sebastian Vettel finished 14th for Aston Martin – the British team back in F1 for the first time in six decades – one spot ahead of Fernando Alonso. Double world champion Alonso (39) has ended a two-year hiatus to make his comeback with the rebranded Alpine team.
Elsewhere, Kimi Raikkonen lost control of his Alfa Romeo through Turn 3 to collide with the barriers before limping back to the pits, while on his debut, Mick Schumacher, the son of seven-time world champion Michael Schumacher, finished 18th, 2.45 seconds off the pace.