Championship leader Lewis Hamilton was in scintillating form as he set the pace for Mercedes in second practice at the United States Grand Prix.
Hamilton’s title rival Sebastian Vettel could manage only third quickest, 0.524 seconds behind the Mercedes, and behind Red Bull’s Max Verstappen.
Hamilton leads Vettel by 59 points and will take the title if he wins the race and the German is lower than fifth.
Vettel suffered a spin at Turn 19, costing him significant track time.
Title win on the cards?
Hamilton has won four of the five races held at the Circuit of the Americas in Austin, Texas, and heads into the weekend on a run of four wins in the past five races.
His form has dramatically turned the championship around, after Vettel had led it all season until Hamilton took the lead with victory in Italy in early September.
Vettel then had a terrible run in the three Asian races, crashing out in Singapore at the start and then hitting engine problems in both Malaysiaand Japan.
Hamilton’s progress in Austin has been serene so far this weekend, the Briton topping both sessions in impressive style.
He was more than 0.5secs quicker than Vettel in the first session, with Bottas 0.6secs slower, the same margin the Finn was behind his team.
A terrible start for Ferrari
In addition to his spin, Vettel also did not manage to complete any kind of race preparation in the second part of the session as Ferrari fiddled with his car in the pits after Vettel complained that the front of the car “felt like jelly”.
He managed to get out with a minute still to go but could only do one lap before the end of the session.
Team-mate Kimi Raikkonen, who was sixth quickest overall behind Bottas and Red Bull’s Daniel Ricciardo, did complete a race run but was 0.5secs slower than the evenly matched Mercedes and Red Bull.
“It was a messy afternoon,” said Vettel. “Not an easy session, but the car is quick so we don’t need to worry.
“The main thing is Kimi did some running. I need to find the rhythm tomorrow. We just need to make sure we get everything in order and it should be a good day.”
Sainz proving his worth
Behind the big three teams, Fernando Alonso was seventh fastest for McLaren ahead of the Williams of Felipe Massa and Force India’s Sergio Perez and Esteban Ocon.
Carlos Sainz made an impressive debut for the Renault team following his switch from Toro Rosso and was 11th, one place and 0.005secs quicker than team-mate Nico Hulkenberg.
New Zealander Brendon Hartley was 17th on his F1 debut for Toro Rosso,1.2secs behind team-mate Daniil Kvyat, who has been drafted back in to replace Sainz for at least one race after being dropped last month.