Red Bull Motorsports Advisor Helmut Marko has detailed why the team fell behind Mercedes during first practice for the Miami Grand Prix.
George Russell put early steering issues behind him to finish top of the session, ahead of teammate Lewis Hamilton and Ferrari's Charles Leclerc.
Max Verstappen was only fourth, despite showing the pace to head his rivals by half a second early in the session.
But whilst the Red Bulls focused on long-run pace following a red flag to clear up the aftermath of Nico Hulkenberg's crash at Turn 3, Mercedes opted to complete the session with low-fuel efforts.
Speaking to ORF and explaining why Red Bull had slumped behind its rivals, Marko said: "It's new asphalt, so then you slide more - we knew that.
"Over the weekend, that will get better. The track evolution will be important here. That had to do with the fact that when Mercedes were doing fast laps, we were doing long runs.
"They also used more power. I believe our set-up for the long run was very good again, because it looked okay for us as well."