Ferrari may test parts for its 2020 engine this weekend in Brazil.
The Maranello team's engine is a hot topic at present, after the FIA in Austin issued a clarification over how the maximum fuel flow is measured.
At the same time, Ferrari's earlier power advantage seemed to vanish.
"The reality is that no one knows why Ferrari was uncompetitive," former world champion Mika Hakkinen told his Unibet column.
"But whatever the reason it will be a focus for improvement for the team as they head into the final races of the season and start to prepare for next year," he added.
Ferrari has denied that the FIA clarification, which came at Red Bull's behest, was the reason for the performance drop in Austin.
Charles Leclerc, however, will have a new power unit fitted in Brazil, following his practice failure in Austin.
According to team boss Mattia Binotto, part of the reason for Leclerc's struggle in Austin was because he used an older and "less powerful" engine in the race due to his practice failure.
"Fitting a new PU means taking a grid penalty in Sao Paulo, but we should be back to our normal performance level and show some fighting spirit to finish the season on a high note," he said.
"That will be important in order to confirm we are making progress with our car and to take some of that momentum into the winter work."
Italy's Autosprint reported that the new engine for Leclerc in Brazil may include "some parts for 2020".
