Toto Wolff has conceded there is "nothing really to see as positive" despite Mercedes showing improved form in the United States and Mexico.
Lewis Hamilton was Max Verstappen's nearest challenger at both the Circuit of the Americas and the Autodromo Hermanos Rodriguez after Mercedes fitted the last of its updates for the remaining rounds of what has been a difficult season.
After struggling to make an impression against Red Bull and Ferrari all year, the Silver Arrows were firmly second-best in Mexico in particular, with Lewis Hamilton runner-up behind Verstappen on both tracks.
The results should provide optimism for an improved challenge from the Brackley-based outfit for next season, but asked how confident he could be over potential wins and even a championship tilt, team principal Wolff insisted: “Never confident.
"I always see the glass as half empty, so there is nothing really to see as positive.
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"Red Bull has had nine wins in a row so there is no reason to be overwhelmed with finishing second and fourth, but we have a long way to catch up. We have the winter.
"We are doing some good development on the car. Some of the things we are finding might be bigger steps than just adding a few points of downforce.
"We are giving it whatever we have and more in order to bring us back in a position to fight for a championship.”
Beating Ferrari a "consolation" but not a priority
Recent results have put Mercedes within touching distance of Ferrari for second in the constructors' championship, with the gap at 40 points with two races to run.
Mercedes chief strategist James Vowles has already suggested that overhauling Ferrari will be "a tremendous ask" given the deficit.
Wolff, though, feels finishing runner-up behind Red Bull would "definitely be some consolation".
He added: "Ferrari had the quickest car at the beginning of the season and finishing ahead of them would be great but again, it is not our main priority.
“Our main priority is understanding the car and having a quick automobile on the track.”