McLaren have admitted that their hopes for the season rely on their major Spanish Grand Prix upgrade following a lacklustre start to the 2018 season.
Although the British team sit third in the Constructors' Standings, the majority of their points have come about through poor reliability and operational problems for their rivals.
In China, Fernando Alonso and Stoffel Vandoorne once again failed to escape Q2 as they qualified 13th and 14th, behind both Renault-powered rivals Red Bull and Renault.
McLaren director Eric Boullier admitted they are unaware of the reason why they're slow in qualifying and why their straight-line speed is lacking compared to their rivals.
"We have the same engine as Renault and Red Bull and we are behind, so there is no hiding, nothing else than fact," he said in Shanghai.
"We need to make the car faster around the corners and in a straight line and we need to understand why we are slow in qualifying, why we are better in the race, and why we are behind the other Renault teams. Full stop.
Boullier though isn't panicking and says they're hopeful it will be addressed with a major upgrade package set to be delivered at the Spanish GP in early-May.
"There were obviously some questions asked in Bahrain, there is still an ongoing process because we have to address it, and we will address it, and we are about to address it.
"I said before we didn't turn up in Australia with the car we wanted, because we were delayed for several reasons," he added.
"A lot of parts and a lot of upgrades are on the way to hit the track. For logistical reasons very likely it's going to be in Barcelona. From that point we'll see performance-wise where we are."
