New Delhi, Feb. 14 -- Mercedes drivers Kimi Antonelli and George Russell were the fastest at the end of three days of Formula 1 preseason testing in Bahrain on Friday.

Antonelli topped the afternoon session, replacing Russell behind the wheel. Russell led the way in the morning as the teams can run only one car on track in the test.

Three more days of testing are scheduled next week in Bahrain, after a secretive "shakedown" test in Spain last month.

Russell said Mercedes still has work to do before the first race of the season, the Australian Grand Prix on March 8.

"Barcelona was very smooth, and probably smoother than we actually anticipated, in terms of reliability, in terms of performance," he said. "We've got to Bahrain and in bot...