Sainz begins life at Williams

The Spaniard concluded his Ferrari stint last Sunday with a second-place finish at the 2024 Abu Dhabi Grand Prix and was soon on his way to Williams as the Italian team agreed to release him early to take part in the post-season F1 test with his new team.

Mercedes, on the other hand, refused to release Lewis Hamilton and allow him to test in Abu Dhabi with Ferrari while Nico Hulkenberg started work with Sauber as Esteban Ocon also was on duty with Haas after being replace by Jack Doohan at Alpine for the season finale in Abu Dhabi.

Sainz made his Williams debut in a filming day on Monday where he was in a white racing suit while his helmet was also plain with no sponsors on it.

The teams will be testing 2025 Pirelli tyres during Tuesday's test with a driver that has a super-license while another car will be allocated to a rookie driver that has fewer than two grand prix starts.

Newly-crowned F1 constructors' champions, McLaren, are fielding Oscar Piastri and Lando Norris for the tyre-testing part while Patricio O'Ward will be their rookie driver.

Ferrari, having missed out on Hamilton, will have Charles Leclerc on tyre testing duty while the rookies driving for the Scuderia are Arthur Leclerc and Antonio Fuoco who drives in Ferrari's WEC program.

Red Bull Racing have Yuki Tsunoda driving their RB20 to test 2025 Pirelli rubber as the Japanese driver is hoping to secure a promotion into the team to replace Sergio Perez.

Isack Hadjar, who drove for Red Bull in FP1 of the Abu Dhabi Grand Prix will be the rookie driver. Hadjar concluded his Formula 2 season second in the standing behind champion Gabriel Bortoleto.

As for Mercedes, Russell will conduct the 2025 tyre compounds' testing while Frederik Vesti and Kimi Antonelli will be the team's rookies.

Antonelli, who will be the team's full time driver in 2025 replacing Hamilton was set to be the only rookie but due to illness, Vesti was brought in.

Aston Martin have reserve driver Felipe Drugovich in the car along with rookie Jak Crawford.

Alpine have Jack Doohan on duty along with the team's new reserve driver Paul Aron.

Haas will be fielding their new-for-2025 driver, Ocon, while Ryo Hirakawa will the US team's rookie driver.

VCARB are fielding Liam Lawson and Ayumu Iwasa.

As mentioned, Williams have Sainz as the tyre tester while their rookie will be Luke Browning who drove their car in FP1 in Abu Dhabi last Friday.

As for Sauber, their will be fielding their 2025 driver lineup, Hulkenberg as the experience driver while F2 champion Bortoleto is the rookie.