Toto Wolff conceded to suffering "a slap in the face" after watching Mercedes' hopes of a potential French Grand Prix victory evaporate in qualifying.
The sense coming into this weekend was that Mercedes would be more competitive, building on the form shown in the double-header at Silverstone and Austria, and with the smooth Paul Ricard Circuit playing into the hands of a more stable W13.
But from the outset in practice, Mercedes has again been found wanting, culminating in Lewis Hamilton finishing almost nine-tenths of a second behind polesitter Charles Leclerc in his Ferrari, with George Russell a further 0.366s further back.
Attempting to sum up the situation, Wolff said: "Expectation management is a bit of a thing this year because we were slowly but surely working our way back to the frontrunners.
"There were good signs in Silverstone, then we went to Austria, a track where we are normally not competitive at all and we could clearly see the signs why we were not competitive, but we were close.
"It's a one-minute circuit and we were three-tenths off in quali, so that was acceptable.
"So we brought a nice update package to Paul Ricard, the track is smooth, off we go, and boom - no performance - and we can't figure out what went wrong."
Wolff explains Hamilton "parachute"
Across the three practice sessions, Mercedes had tried a number of rear wings on Hamilton's W13 with the seven-time champion gradually adding extra downforce.
But the cost was too great on a straight line and he converged with Russell for qualifying.
"We experimented with rear wings, from almost the biggest we have, which Lewis described as dragging a parachute behind him, to a smaller version which makes us lose too much speed in the corners," explained Wolff.
"Then we were experimenting with tyre temperatures, and you could see it [the gap] went from seven-tenths to 1.2 seconds so that is a bit of an outlier.
"If you had told me we would be ending up between seven-tenths and...how much are we off [told Lewis 0.9s off], yeah, that's a bit of a slap in the face."