World champion Lewis Hamilton says rivals Red Bull will be a “different animal” in this year’s title after the conclusion of pre-season testing.
Red Bull’s Max Verstappen was fastest after testing in Bahrain, which hosts the first race on 26-28 March.
Mercedes driver Hamilton said: “Red Bull have had some really good running. Both drivers have been looking strong.
“They are going to be a different animal this year. A strong line-up with the two drivers and a really good car.”
Hamilton had a spin on the final day of testing and set the fourth fastest time, also behind Alpha Tauri’s Japanese rookie Yuki Tsunoda and new Ferrari signing Carlos Sainz.
Verstappen’s new team-mate Sergio Perez set the fastest time of the morning session before handing over to the Dutchman for the afternoon one, in which track conditions were faster.
Headline times in pre-season testing are notoriously unreliable as indicators of competitiveness as it is impossible to know the specification in which cars are running, and fuel loads and engine modes make significant differences to lap time.
Nevertheless, Red Bull have looked more convincing than Mercedes, whose test has been hampered by reliability problems and concerns over the balance and stability of their car.
Hamilton also pointed to the fact that Verstappen won the final race of last season, a more relevant point than usual as teams have been forced to carry over large parts of their cars from last year as a cost-saving move in the pandemic.
Hamilton said: “Having won the last race, you can only assume they are going to be right there if not at the front at the first race and it is going to be a great long battle with them through the year.”
Verstappen said: “I had positive feelings in the car but we will find out at the first race where we are. It has been a good few days now but we always improve and try to be better.”
Hamilton’s team-mate Valtteri Bottas said Mercedes had made progress with their car after a difficult first day, when the Finn lost running with a gearbox problem and Hamilton suffered handling problems.
“It feels like we have made made some steps forward,” Bottas said.
“We went in the right direction and it felt better. Still not 100% happy with the car, as you would never be at this early stage of the season.
“We keep working and trying to get the balance better and the car behaving nicer and that way be faster. It is completely unknown where we are at the moment after three days of testing. With the first day being compromised, it is so hard to say.
“I have a feeling it is going to be close.”
The Aston Martin team, formerly known as Racing Point, had a difficult test, with new signing Sebastian Vettel particularly badly hit by reliability problems, and an engine issue on the final day restricting him to a total of just 117 laps over three days.