Helmut Marko has pinpointed the Canadian Grand Prix as the race which should provide the "biggest step" for Red Bull this season and warned they have "a lot of work to do".
Max Verstappen finished fifth in the season-opening Australian Grand Prix and Daniel Ricciardo was unable to finish in his homeland on Sunday.
Red Bull are awaiting an upgrade to their Renault engine and the team's motorsport advisor Marko does not expect any quick fixes.
"There's a lot of work to do," Marko told Motorsport.com.
"The race speed makes us think positively. But from our side, there is a lot to do, and Renault's side as well.
"Montreal is their biggest step. Something smaller is coming in Barcelona, but a reasonable step in Montreal."
Marko, however, is optimistic that engine upgrades can have a significant impact for Red Bull.
"We hope so, if we improve our chassis dramatically as well," he added. "Our engineers think so and the simulations say so, also."