Though Mercedes dominated the first three seasons of the new formula, winning all but a handful of the 59 Grands Prix, this season its clearly faces stiffer opposition than at any other time.

However, over the course of those three magnificent seasons of domination, there were times when the German team appeared to lose the plot, the most significant example being Singapore 2015.

While the German team looked to be the class of the field in FP1 yesterday, in the second session both drivers were clearly struggling.

Though tyre issues are nothing new for the German team, to see Lewis Hamilton and Valtteri Bottas eighth and tenth however, both over a second off the pace, was something of a shock, to put it mildly.

After all, Monaco is the one race where one really has to be on the front row or else heed Dante's advice and abandon all hope.

While there was already concern that the Mercedes long wheelbase might compromise the team, Toto Wolff claimed it was a change in set-up that was at the root of the problem.

"We took a wrong junction in setting up the car in a direction which we believed was good," he admitted. "We couldn't back out of it. We committed to the set-up as it takes longer than a session to change and we decided to push through and collect some data.

"There was a lack of grip and we went out of the window everywhere," he continued. "We were pretty competitive in the morning and we just need to back track it. That's not a very difficult exercise but we lost a session where we could have progressed. We are lacking data so it's about sticking our heads together, staying calm and trying to work as well as possible on Saturday morning."

Though Lewis Hamilton more or less echoed Wolff's comments, a concerned looking Valtteri Bottas admitted that he "hoped" set-up was the problem. Got that, "hoped". Fact is, the Finn didn't look entirely convinced.

While, over the course of those three seasons Mercedes would frustratingly play down their chances, insisting that - despite having finished 1-2 in the previous three races - they were concerned at what the opposition might have up its sleeve - this year those looks of concern are genuine.

Not for one moment are we suggesting that the German team's reign is over - though all such reigns must come to an end eventually - however, the fact is from now on when Wolff plays down his team's chances he's not bullsh*tting.

Check out our Thursday gallery from Monaco, here.