MONTREAL, Canada -- Mercedes' technical director James Allison believes championship leaders Red Bull may have made a step backward with a recent car upgrade.
After a dominant start to the season, Red Bull has won just one of the last three races despite introducing an upgrade package at the Emilia-Romagna Grand Prix last month.
Max Verstappen still won the race at Imola in the upgraded RB20, but his victory margin was the smallest of the season at just 0.7 seconds over McLaren's Lando Norris.
Allison expects Red Bull will rediscover its form from the Spanish Grand Prix onwards, when F1 returns to circuits that are more likely to suit the RB20, but said the championship-leading team could become vulnerable if it has taken a wrong turn with its development.
"My guess is that as soon as there's a decent range of cornering speeds, they will be useful again," Allison said of Red Bull. "But it does look as if their upgrade was a downgrade, so fingers crossed that will really f--- them up.
"That makes life hard because the moment you stop trusting your tools, you back track and you start losing time. And time is your biggest friend and losing it is your worst enemy."
Mercedes has looked like the fourth fastest team at recent races, but after a series of upgrades in Imola, Monaco and again ahead of this weekend in Montreal, Allison believes his team is now just a small step away from fighting at the front.
"Where we are now seems to be better than where we were two races ago," he added. "Hopefully it will be somewhat better in a couple of races from now.
"We've gone from being really embarrassingly crap or not good enough in the beginning of the year, to being near the fight.
"A little bit more will get us right in the melee."