The Mercedes pair could not make their tyres last at the Autodromo Hermanos Rodriguez, with Hamilton finishing over a minute down on race winner Max Verstappen in fourth and Valtteri Bottas ending up a lap down.
Team boss Toto Wolff had “no explanation” for the Silver Arrows’ sudden woes after the Mexico race – although he dismissed the team’s decision not to use its controversial wheel rim design as a potential factor.
And while Hamilton confirmed ahead of the Brazilian Grand Prix that Mercedes has made progress in understanding its slump, he conceded its problem wasn’t fully resolved.
“I think some of it is still a mystery, but I think there’s a lot of areas that we’ve understood,” Hamilton said.
“We’ve come to another circuit which is quite hard on the tyres, Brazil is always quite tough in that area, but we’ve not been terrible here.
“I’m hoping this weekend we can get the car into the right place, so we can fight the Red Bulls and the Ferraris, who have seemed to come back more into shooting range.
“Red Bull’s dominance in the last races was impressive, and I’m sure they’ll be quick here this weekend as well, as will Ferrari. So it’s going to take everything and more [to beat them].”
Teammate Valtteri Bottas said Mercedes was now aware of the “mistakes” it has made that led to its Mexico disappointment.
“The team worked really hard on that in terms of finding answers quickly,” Bottas said. “I went to the factory and had a meeting about it – it’s been really interesting to see how we’ve been able to track those issues.
“It is about how we’re managing the tyres, we know we’ve made mistakes and we hope not to repeat them.”
While Hamilton isn’t confident the work undertaken after Mexico will instantly eradicate Mercedes’ problems, he reckoned it could be crucial for 2019.
“It might still take this race or even next race before we fully understand it,” he said.
“I think it just points to the fact that there’s still always lots of work to do, even at this point in the year there’s still things you can learn from and improve, or methods that you can apply to next year particularly which are going to be quite important.
“I think, even though they [USA and Mexico] have not been great races, I think they’ve been quite a steep learning curve for us.”
Lewis Hamilton, Mercedes AMG F1 W09 EQ Power+, leads Valtteri Bottas, Mercedes AMG F1 W09 EQ Power+
Photo by: Steve Etherington / LAT Images