Lewis Hamilton and George Russell had been hoping that a strong performance in last week's Mexican GP meant that Mercedes were going in the right direction in its battle to get back into race- and title-winning contention.
But a disappointing showing in today's Sao Paulo Sprint at Interlagos - one of Hamilton's favourite and most successful circuits - has left them feeling confused and unhappy once more, after Hamilton dropped from fifth to seventh.
"The last couple of races we've been excited that we're progressing, and it's been really positive to see," Hamilton said after the race. "And you come to another track and then you have the worst [tyre degradation] that you've had for ages.
"It's like you just don't know what to expect with this one," he complained, adding he would be happy to see the back of the W14. "Only a couple more races with this car and it's gone, and I'll be happy! Counting down the days."
Hamilton said that balance had been the key issue today. "We tried to get the right balance with the wing, just a lot of understeer, snap oversteer, and the rear tyres just dropped off. And in the mid-sector, huge understeer.
"I don't know whether we got the set-up wrong. We probably got the set-up wrong," he sighed. "But it is what it is."
Team principal Toto Wolff admitted this had been "a bruising day" for everyone at Mercedes. “It was very odd. Everything went against us today.
"We need to really scratch our head hard for what we can do tomorrow and improve [but] I don't think there is a magic screw you can turn and then everything is fixed.
“I think we had a little bit too weak of a rear end,” he told Sky Sports F1. "Obviously it's balancing them on the knife's edge. Trying to hold onto the pace is maybe something we need to learn for tomorrow."
Russell had started from fourth and flew past Sergio Perez at the start, and then overtook Lando Norris later on the opening lap to move into second behind race leader Max Verstappen.
But over the next ten laps all that early momentum vanished, with Norris and Perez regaining their places leaving Russell crossing the line where he had started, off the podium in fourth.
"It was a good start. Sort of had that Turn 10 lined up as an overtaking opportunity,” Russell told the media in the paddock at Autódromo José Carlos Pace after the end of the 24-lap Sprint.
"We were fast in Turn 8/9 and I thought that was my chance, so glad to make that stick," he continued. "Just a shame we went backwards.
"Really unexpected," he replied when asked if he had expected to drop off the pace like that. "We didn’t expect to be the fastest, we thought we’d be a couple of tenths behind Max, maybe similar pace to Lando.
“We’re the slowest on the straight at the moment, so we’re very vulnerable if anybody gets DRS behind us," he pointed out. "We knew that was going to be the case here, but that wasn’t the reason for our lack of pace.
“But clearly we got something wrong today. As always it’s down to tyres. Tyres just dropped off. Story of everybody’s season, and we need to rectify it because that was a disappointing one.
“If anything, being on probably a bit more downforce than everybody else, we were expecting to have less tyre deg. We really need to understand what went wrong," he said. "But it’s a bit of black magic.”
Because of parc ferme conditions, it's too late for the team to make significant set-up changes for Sunday's Grand Prix but Russell said that wasn't necessarily the end of their hopes.
“If it’s going to be four or five degrees colder tomorrow, that might transform everything. Not all is lost yet!"
Keep up to date with all the F1 news via Facebook and Twitter
