McLaren is banking on a significant Barcelona upgrade package to boost its performance, but racing director Eric Boullier is also expecting rival teams to move forward next week.
The Woking-based outfit's relative performance has been a disappointment so far this season, its first with engine partner Renault.
While the team's resurgence has perhaps fallen short of expectations, McLaren has been a consistent points-scorer since Melbourne, leaving the team fourth in the Constructor's standings and "best of the rest" behind the sport's dominant trio of front-runners.
Boullier hopes a highly modified MCL33 will allow F1's second most successful team to close in on its rivals ahead, but much will depend on its peers own progress in the next week.
"There is a new direction for Barcelona, but you cannot expect us to leap ahead of everyone else," warned Boullier.
"I think 95 per cent of the paddock will bring new aerodynamic packages to Barcelona, so the difference will either be the same, we lose some ground, or perhaps we gain a little," he told El Confidencial newspaper.
"It is up to us that our evolution works and lives up to our own expectations, and then to hope that the others cannot do the same," said Boullier.