Ferrari's dominant win at the Canadian Grand Prix has alerted Mercedes to the new reality it is facing in 2018, according to team boss Toto Wolff.
The nature of the power-sensitive Circuit Gilles Villeneuve meant Mercedes arrived in Montreal as favourites, although the decision to delay its engine upgrade until the next race in France appeared to swing the initiative back in Ferrari's direction. Sebastian Vettel ended up snatching pole from Valtteri Bottas on Saturday and then turned in a comfortable performance to win the grand prix on Sunday, taking the championship lead from Lewis Hamilton in the process.
It means Mercedes, Ferrari and Red Bull have each won one of the last three races and Wolff expects the pendulum between the top three teams to keep swinging back and forth.
"There's not really a pattern that you can see," he said. "Normally, on some tracks, we were dominant and then others we struggled. Then somehow this year, the margins have become so tight that if you look at the fastest lap, there's five cars within a tenth [of a second].
"This is why this year's world championship will be decided by the team who makes the least mistakes, brings the best development on the engine every single weekend. That is the new reality. Six cars can win races. It's a three-way fight.
"You can't take anything for granted and think it will be a walk in the park. That's the kind of wake-up call you get."
Wolff was puzzled by the fact Mercedes never looked like putting Vettel under pressure during the grand prix.
When asked if he was worried errors could start creeping in as a result of an intense fight, he said: "I think you need to get the right balance between pushing development very hard, adding performance to the car and at the same time keeping reliability.
"This team has been extremely strong in the past, keeping the reliability at a high level. That is not the part that worries me. It is more that we have seen today a Ferrari that has been the stronger car, stronger in qualifying, stronger in the race, and at no time did we have a real chance to fight for the win."