Max Verstappen finished half a second adrift in sixth in Thursday's FP2, which was held in similar night-time conditions as qualifying and the race, with team-mate Sergio Perez a further three tenths behind in 10th.
Meanwhile, Mercedes stole the headlines with a 1-2 for Lewis Hamilton and George Russell. But while Red Bull admits its qualifying pace is not looking as strong as it would have liked, Verstappen believes lower engines modes are responsible for the gap to Hamilton.
"I think it was not too bad, it was very close," Verstappen said. "Maybe some people around us already turned up the engine a bit in terms of top speed.
"I don't say everyone around us did that but a few did, so I'm not too worried about the gap to P1, for example. But it's going to be very close in qualifying, so that's going to be very nice."
When team advisor Marko was asked by Motorsport.com/Autosport if Red Bull was on the bottom end of engine mapping compared to its rivals, he replied: "Yes. Not everybody is using the same engine mapping, so we are not worried.
"Today it didn't come as easy as during the tests. The long run was good, but qualifying will be very tight."
Mercedes and Ferrari both particularly impressed with one-lap speed, while Verstappen says he hadn't yet been able to hit the sweet spot on the RB20's balance.
But amid all the excitement over a tighter grid in qualifying, Red Bull still looked ominously dominant in race simulations, which has long been its focus on grand prix weekends.
"There were a few little balance issues from front and rear, but nothing big," he explained.
"It's just about trying to find that sweet spot. Especially around here with the rough tarmac, once you find that sweet spot you just pick up time and that's what we'll try to focus on.
"It's not too far away, just trying to get into it and feel a little bit happier with the car. But you also want to focus a bit on the long run because that's where the car really needs to work.
"Of course, qualifying is also important but we need to make sure the car is in good shape for the race."
Additional reporting by Ronald Vording
