Lewis Hamilton only fourth in final Abu Dhabi practice
Title rivals Lewis Hamilton and Nico Rosberg were only fourth and fifth quickest in final practice at the season-ending Abu Dhabi Grand Prix.
Ferrari's Sebastian Vettel set the pace, 0.137 seconds ahead of Red Bull's Max Verstappen with Vettel's team-mate Kimi Raikkonen third.
Hamilton maintained the advantage over Mercedes team-mate Rosberg he has had all weekend, lapping 0.103secs quicker.
But their rivals' pace gives Hamilton hope others may mix it with Mercedes.
That is what the Briton needs if he is to wrest the title from Rosberg, who has an advantage of 12 points.
Hamilton needs to win the race with Rosberg finishing lower than third if he is to overturn the German's lead.
It would still, though, be a major surprise if Hamilton and Rosberg were not in a private battle for pole position when qualifying starts at 17:00 local time (13:00 GMT).
McLaren driver Fernando Alonso, who was 11th fastest, said: "Mercedes have been dominating quite easily every single race of the year so I don't expect coming to the final race someone putting a lot of pressure on them. I expect first and second for the Mercedes in qualifying and first and second on Sunday."
Hamilton ended final practice 0.103secs quicker than Rosberg and 0.290secs slower than Vettel.
A genuine challenge to Mercedes would be a surprise, but Ferrari do appear to be having a good weekend and it cannot be completely ruled out.
However, the Ferrari drivers and Verstappen all set their fastest times later in the session than Mercedes ran their qualifying simulations on ultra-soft tyres.
This would give Ferrari and Red Bull an advantage because the track would be quicker.
When they were out at the same time, Mercedes were more than half a second quicker than Ferrari and Red Bull.
Verstappen's team-mate Daniel Ricciardo may therefore be a more reliable indicator of the competitiveness of Mercedes' rivals - he was 0.663secs behind Rosberg in sixth place.
The Force Indias of Sergio Perez and Nico Hulkenberg were seventh and eighth, ahead of Esteban Gutierrez's Haas, McLaren's Fernando Alonso and Renault's Jolyon Palmer.
Jenson Button's final grand prix has improved after a difficult start. He had a troubled Friday with limited running because of an engine problem, but the 2009 world champion was 13th quickest, just 0.079secs behind team-mate Alonso in final practice.