McLaren is targeting a coveted sixth place in the 2019 drivers' world championship with Carlos Sainz.
With Mercedes, Ferrari and Red Bull dominating the top six places, the most any other driver can realistically expect from a race and championship is the 'best of the rest' seventh.
But Spaniard Sainz, who is regularly 'best of the rest' in 2019, is now just five points behind Red Bull's struggling second driver Pierre Gasly.
"The only driver he can reach is Gasly and we will try to make it happen," McLaren boss Andreas Seidl told AS newspaper.
"Although the Red Bull is a significantly faster car than ours, and it will be difficult, we will not stop trying," he added.
Seidl, who is McLaren's new team boss, admits he has been impressed with Sainz in 2019. But he stopped short of saying Red Bull was wrong to let him go.
"I can't judge what happened in the past, but we are happy with the two drivers we have," he said, also referring to Lando Norris. "That's why we announced them so soon for 2020."
