The Silver Arrows camp arrived in Melbourne optimistic about taking a “huge step forward”, with Lewis Hamilton defending the W15 as an “amazing car” and not being an “evil sister”.
This followed driver complaints that the team was falling back in the opening races of the new year, with Mercedes starting strongly in free practice only to regress in qualifying and the race.
But Mercedes motorsport boss Wolff called out a difficult Friday showing in Melbourne after his drivers slipped from third (George Russell) and ninth (Hamilton) in FP1 to sixth and 18th.
Laying the blame with extreme set-up changes between the two sessions that “massively backfired”, the Austrian told Sky Sports: “We’ve achieved the experiments, but we haven't unlocked performance.
“In the second session, we have gone through a really quite dramatic set-up change on Lewis. That has massively backfired. But this is why we are having those sessions.
“On the other side [with Russell], it was a bit better. But we are lacking performance.
“I think on a single lap, if you finish a set lap, we are a bit better. But overall, it wasn't a good thing.
He added that Mercedes still had all the tools at its disposal to regain competitiveness during the current rules era, saying: “If I would say that I'm not frustrated, it would be not the truth.
“Certainly we are because we're trying so much in all directions, but don't seem to have found that silver bullet yet, which helps us to get us in the right direction.
“But we've got to keep trying. We've seen performance in this car before.
“I just don't want to go back and say we're just not good in these [ground-effect] regulations, because we have everything we need in order to get on top of that. And we will.”
Mercedes trackside engineering director Andrew Shovlin reckoned the bigger-scale performance tweaks to improve in high-speed corners and cut the bouncing from Saudi Arabia had worked, despite the FP2 struggles.
He reflected: “We had a good FP1 session. The changes we made to improve our high-speed cornering performance and reduce the bouncing after Saudi Arabia seemed to be a good step in the right direction. Overall, the car was feeling quite good.
“Unfortunately, FP2 wasn't as strong. Lewis felt that we had gone in the wrong direction with our changes. Frustratingly, they weren't quick to unwind so he had to live with that throughout the session.
“George found the car a bit trickier in the windier conditions of FP2 compared to earlier in the day. We could have ended a bit higher up the time sheets had he not had a bit of damage. Overall though, it’s clear that we've got work to do overnight to improve the car.”
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