Max Verstappen's rivals fear Red Bull could be too strong for them on a traditional racing circuit at this weekend's Spanish Grand Prix.
Red Bull started the season in dominant form but haven't had things all their own way in recent weeks. McLaren and Ferrari have won races since the start of May while Mercedes joined the fight for the win last time out in Montreal.
But after a flurry of street tracks, F1 returns to more traditional circuits for the next few rounds, including this weekend's race in Barcelona. And Red Bull are expected to be stronger as a result after struggling on bumps and kerbs in recent weeks.
McLaren's Oscar Piastri thinks his team will "be in the fight" but backed Red Bull to flex their muscles on a track with a mix of cornering speeds. The Australian said: "I think we can still be confident, definitely.
"I wouldn't say we're weak in high speed, it's just that others probably caught up a little bit. So we'll see. I'm pretty comfortable we'll be somewhere towards the front. As well, I think Red Bull will probably be a bit stronger than they have been. But I think we'll be in the fight."
Ferrari racer Charles Leclerc has a similar outlook ahead of the Spain race and told reporters: "I feel like the strength of Red Bull will be more visible on a track like Barcelona, but let's wait and see. And behind, I think we'll all be pretty close."
Mercedes had to watch in with envy earlier this year as their rivals took the fight to Red Bull. But in Canada George Russell qualified on pole and finished third, while Lewis Hamilton also looked strong on race day as the Silver Arrows' car upgrades did the business.
For team principal Toto Wolff, the Barcelona circuit will provide the litmus test to measure whether Mercedes really are closing in on the top teams. He said: "We have continued to make incremental gains across the past few races. It was encouraging therefore to take another positive step forward in Canada.
"To see that translate into our strongest team result of the season so far is a reward for everyone's hard work. The Circuit Gilles Villeneuve is a unique track, however. It has a narrow range of corner speeds and, with a newly re-laid surface, was something of an outlier compared to more traditional venues. We know our competitors will perform more strongly at upcoming races so we will need to continue to work hard to consistently get ourselves in the fight for podiums, and eventually, race wins.
"Barcelona will provide a good test of our progress. It has a mix of fast, medium, and low-speed corners, a long straight, and plenty of elevation change. Tracks that contain this wide speed range have been a weakness of ours so far this year. This weekend will therefore provide another opportunity to evaluate our progress through our recent updates, and we hope to build on the positive momentum from Montreal."
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