Canada was a spanner in the works in Mercedes' otherwise flawless 2014 campaign.
"You quickly get used to winning," team boss Toto Wolff told Spanish reporters at the team's Brackley headquarters this week.
"I never thought, unless there was a collision, that we could not finish a race even with one driver. But in Montreal it was about to happen," he is quoted by EFE news agency.
"It was a good wake-up call."
The most immediate problem for Mercedes is getting to the bottom of the technical glitch.
Germany's Bild newspaper reports that the issue can basically be traced to the energy recovery systems, which overheated.
Wolff said: "In Montreal, we were trying a new cooling system for the first time. The new software went crazy."
Team chairman Niki Lauda added: "It is a wake-up call. We need to check every detail on the car."
Wolff continued: "We have started new processes of quality control to make the car more reliable."
But another issue to consider is the intense driver rivalry between Hamilton and Rosberg, who until now have appeared to have no external competitors for the 2014 crown.
Wolff was asked this week if, given his Canada DNF, the new 'double points' innovation for the 2014 season finale might be Hamilton's saving grace.
"It might," the Austrian is quoted by Italy's Tuttosport, "but I have no doubt that, first of all, we must be careful to keep our gap to our rivals.
"Red Bull scored a lot of points in Canada," Wolff added.
As their personal battle waged in the most recent weeks, Mercedes' drivers have been told repeatedly that the Brackley team's main goal is actually the constructors' title.
But until now, Mercedes has let Rosberg and Hamilton wage their war almost unfettered, despite the risk of a crash.
"The team management is handling the situation very well," Hamilton told Germany's Sport Bild this week. "You have to realise that their ultimate goal is the constructors' title. That's what brings in the money.
"The team is number one," the Briton insisted. "Only after that do Nico and I have our personal battle."
At Monaco, however, that appeared not to be the case, as Hamilton had what many described as a 'tantrum', siding with those who believed Rosberg had committed a deliberate act of sabotage in qualifying.
Hamilton says now: "I called Nico, we talked about Monaco and the situation is resolved.
"It was really important for both of us to show the team that we can continue to work well together."
For Hamilton in particular, given his now 22-point deficit to Rosberg, the obvious fear is that Mercedes will end the 'free fight' between the drivers in the wake of the escalating driver battle and, now, reliability fears.
Wolff, however, rejected the theory that the reliability problems last week in Canada were caused by Hamilton and Rosberg pushing their cars too hard in battle.
"The damage would have occurred even if they had slowed down," he insists.
Wolff told Sport Bild: "We told the drivers how to manage it by changing the brake balance and braking more carefully. Both of them did it exactly to our specifications.
"That what happened to Lewis did not also happen to Nico was just pure luck."
Nonetheless, Wolff admitted that Mercedes' situation in mid-June is giving the team pause to "question whether we can let them continue to race so freely".
He is quoted by the Spanish daily AS: "We will continue to let them compete and fight as long as it does not undermine Mercedes.
"We are a F1 team, not a team of two F1 drivers," Wolff insisted. "We are all rowing in the same direction and share the same goal, which is simply to win the title.
"At the moment they continue to race freely, although the situation may change at any time. This is an ongoing, dynamic process," he added.
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