McLaren has had a tougher than expected start to the 2018 season after admitting it missed its initial development targets.

The team's racing director Eric Boullier then declared the Spanish GP, traditionally the first time teams can produce significant revisions to their 2018 challengers, as the place to see McLaren's "real" 2018 car.

McLaren has downplayed its expectations for the upgrades since then, but Alonso said: "In Barcelona there is a new aero package coming, but I think 95% of the paddock is bringing a new aero package to Barcelona.

"So, maybe the gap remains as it is, or we just recover a little bit, or we lose more ground.

"Who knows? I think it is up to us to make that package work to expectations and hopefully some others, they don't deliver. That is our hope."

Alonso finished seventh in Azerbaijan last weekend despite keeping up McLaren's unwanted run of qualifying outside of the top 10 for every race this season so far.

The team's Saturday form is its biggest weakness at the moment, with opportunistic Sunday performances putting Alonso sixth in the drivers' championship and McLaren fourth in the constructors' contest despite the tricky start.

Boullier said McLaren has been "bringing parts every weekend" in a bid to boost performance.

"There is a new direction maybe starting from Barcelona and you cannot expect, as Fernando said, to jump up everybody," said Boullier.

"Everybody is bringing parts, everybody is bringing a package, especially for the first European races.

"Monaco will be another upgrade, Canada will be another upgrade and Silverstone as well. It is every race."

McLaren is one point ahead of Renault's works team in the constructors' championship despite being unable to match its engine supplier's outright performance.

Asked by Motorsport.com if Renault needed to worry about McLaren's Spanish GP upgrade, Carlos Sainz replied: "I think you always need to worry about McLaren.

"That team has such a history and such a rate of development, I think you always need to keep an eye on them.

"McLaren have not showed a great pace in qualifying but I tell you in the race it is a different car. They look very strong.

"At any moment they could find those two tenths in qualifying and start putting us in a difficult position."