Fernando Alonso has described McLaren's 2017 Formula 1 season as "very bad", despite successfully developing a car he has previously called the best on the grid.
McLaren has endured a disappointing third F1 season in partnership with Honda, suffering a lack of power, reliability and results that leave it languishing ninth in the constructors' championship with two races to go.
Successful aerodynamic development of its 2017 chassis has left McLaren feeling it is close to matching Red Bull on certain circuits and "giggling" with excitement about its prospects for 2018 when it switches to customer Renault engines.
When asked for his assessment of the season so far, Alonso said: "It was very bad.
"It was not a good season, despite the progress that is noticeable we did with the car, and despite the optimism for next year.
"We all believe inside the team it will be a fantastic 2018 season - we have a better mood now in the team.
"[But] if we look back and we launch the car in McLaren in February - new regulations, four months to work on the engine, to power a little bit what we had in 2016, the hopes for this season were much different, from myself and from the team.
"Now, to be ninth in the constructors' championship, to use nine engines until now, it cannot be a good season for anyone in the team."
Alonso reckons the Mexican GP, where he showed competitive qualifying pace before sitting out Q2 because of a grid penalty then fought wheel-to-wheel with Lewis Hamilton in the race, was McLaren's "best race" of 2017.
Team-mate Stoffel Vandoorne will now also use McLaren's latest update package, introduced on Alonso's car two races ago, and Alonso feels Brazil will indicate whether McLaren's strong Mexico form was merely track specific.
"So far Mexico has been our best race," he added.
"We didn't have any big things coming for Mexico, because it was only four days after Austin, so it could be just track specific. We need to see here in Brazil.
"But from Hungary onwards every step we introduced on the car was quite positive - even if in Spa, Monza, because of the layout we didn't prove it, I think we are in the right direction.
"Definitely still a little bit [needed] to catch the top guys, in terms of also the chassis, but we are now optimistic.
"We know our strengths, we know our weakness, and we need to make sure that in March next year we attack all of them."