McLaren unveiled a radical new nose for its 2018 car in Barcelona.
It follows a disappointing start to the season for the British team, despite the switch from Honda to Renault power.
"Definitely we are not in the position we wanted or expected," Fernando Alonso admitted on Thursday.
Although McLaren aimed to be with the top teams in 2018, the Spaniard said that the car is actually "1.8 to 2 seconds behind".
It has triggered speculation the 36-year-old, who is already combining F1 with Le Mans in 2018, will quit completely at the end of the year.
"The biggest problem is how predictable everything is. The direction everything went is sad for formula one," Alonso said in Barcelona.
Also hoping that McLaren can improve with its 'B' car this weekend is Alonso's teammate, Stoffel Vandoorne.
"My personal feeling in the car is not 100 per cent good," he told RTBF television.
"It's difficult to extract everything from myself and the car. I hope these new parts will help us to move things in the right direction."
McLaren are fourth in the team rankings ahead of the race in Barcelona.