Fernando Alonso and Carlos Sainz have accused Mercedes of exaggerating their lack of pace after George Russell and Lewis Hamilton challenged Max Verstappen for Australian Grand Prix pole.
Russell and Hamilton have expressed frustrations over the performance of the W14 after Mercedes failed to compete with Red Bull the opening two races of the season, while team principal Toto Wolff has confirmed plans are under way to drastically change their design philosophy.
However, the British duo suddenly sprung into contention for pole at a cool and windy Albert Park on Saturday, before ultimately missing out to Verstappen.
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Alonso, who has finished on the podium behind Red Bull one-twos at each of the first two races of the season, was fourth for Aston Martin, while his fellow Spaniard Sainz was fifth for Ferrari.
Asked by Sky Sports F1's Rachel Brookes if he was surprised by Mercedes' pace, Alonso said: "Not really. I think they were very fast in Jeddah already and they were fast in P2.
"They are always fast. If you read their comments, it seems they have a car that is (going) out of Q3, but it is not that car."
Sainz, who was being interviewed alongside his compatriot, added: "I agree. They are a lot faster than people think, I think, especially in the race.
"In Jeddah, in the race they had a pace very close to Fernando.
"Lewis and George, they were flat out and we couldn't keep up with them.
"So that car is quick. It's clearly not as quick as the Red Bull, no one is, but if they put Qualifying together, they can actually be a very strong package too."
Alonso urges Mercedes to 'stop Max somehow'
While Alonso appears to be unimpressed by Mercedes' handling of their start to the season, the 41-year-old urged his rivals to make life difficult for Verstappen, who sits at the top of the drivers' standings as he chases a third successive world championship.
The Dutchman, who is seeking a first Australian Grand Prix victory, is the lone Red Bull at the front of the grid after team-mate Sergio Perez's error in Q1 left him starting last.
"Let's see at least if the Mercedes can make a good start and stop Max somehow," Alonso said. "If not, it's going to be a boring race for him."
Saturday's dramatic Qualifying continued what has been a chaotic weekend in Melbourne, with red flag interruptions and bad weather having earlier prevented teams from getting through their usual race simulations in practice.
As a result, Alonso believes there is additional mystery going into Sunday's race, which is live on Sky Sports at 6am.
"I think there are many unknowns going into the race after missing FP2, and also the temperature, I think, is going to be very different tomorrow - it's supposed to be sunny," he said.
"So I think in terms of strategy and race preparation, no one is fully ready yet, so I think tomorrow is a race where we will discover who has better pace and better management."
Leclerc: Miscommunications cost Ferrari
Charles Leclerc, who will start Sunday's Grand Prix from seventh, admitted that Ferrari's Q3 was hampered by a miscommunication with his team-mate Sainz, but he also laid blame at his own feet for being unable to "put everything together".
"Q1 and Q2, clearly, I wasn't on it. I wasn't driving well. I wasn't putting everything together, so that was my fault," said Leclerc.
"Q3, I managed to fare a bit better. In the car, I was quite confident I could put everything together.
"Unfortunately, I don't know what happened in the second run of Q3, whether it was a miscommunication with Carlos or whatever.
"But I found myself behind him for the whole first sector, which wasn't great.
"We'll speak at the debrief about that to try and improve those situations.
"So, it's a bit my fault because when you arrive to Q3 you need to put everything together in whatever laps you do.
"We could have optimised it by having a better communication. But I also didn't do a great job today."
Watch the Australian Grand Prix live on Sky Sports F1 with lights out at 6am on Sunday April 2. Get Sky Sports