Mercedes Formula 1 driver Lewis Hamilton has suggested the rival Ferrari cars were "sandbagging" in Friday practice ahead of the Spanish Grand Prix.
The Silver Arrows swept opening-day running, with Valtteri Bottas quickest in FP1 and Hamilton setting FP2 pace, while Ferrari – on a run of three straight poles with Sebastian Vettel – was slowest of the three leading teams.
Vettel, the faster of the two Scuderia cars in both sessions, was 0.95s off the pace in FP1 before improving to 0.326s adrift in the afternoon.
Hamilton, however, was not convinced Ferrari's form has dropped off.
"I think it's still very close," he said. "Not really quite sure where Ferrari's pace was today, but they're probably sandbagging, or something, they'll bring it out tomorrow.
"The Red Bull's obviously very close to my pace, so I think, again, it's going to be relatively close between the top three teams.
"I can't really tell you which one's quickest at the moment - because again, fueling [levels] and maybe one didn't get their lap or something like that, tomorrow we'll get a much better understanding."
Teammate Bottas offered a similar assessment to Hamilton's, saying: "Things can really change from Friday to Saturday, we know that Ferrari is still going to be there tomorrow, and Red Bull looks quick."
Vettel, for his part, stressed that he pushed for the best possible laptime on Friday, and insisted that overnight improvements would not "come for free".
"You always try to go as fast as you can," he said. "Usually we're able to find some performance overnight so we'll try to do the same for tomorrow.
"It doesn't come for free, we have to work for it.
"We can improve, I know there's a little bit more in the car and a little bit more in me if I get everything together. It should be OK tomorrow, where we end up I don't know. It could be P1 or P6."
Vettel said the updates brought by Ferrari to Spain – which included the mounting of the mirrors to the halo and tweaks to the SF71H's floor – all "seemed to work".
"The car's OK, the updates are working, I can feel the car is better," he said. "The biggest change came from the tyres, they seem to be quite a bit different."
Pirelli has elected to bring tyres with a thinner tread to Barcelona – as well as the Paul Ricard and Silverstone F1 races later in the year – and Hamilton said he, like Vettel, noticed the difference with the Spanish GP specification.
"I think the race is going to be interesting, just with the tyres," he said.
"We've got much different tyres this weekend, given that there's less rubber on them, so they're feeling just different, sliding a lot more."
Additional reporting by Scott Mitchell