Pierre Gasly kickstarted his team's second week of testing with a productive day in Barcelona, but the Frenchman insists Red Bull's rivals are likely playing their cards close to their chest.
Gasly was the day's marathon runner, clocking in with 136 laps and the second fastest time.
As Red Bull finally showed a bit of its hand in pre-season testing, Gasly was a solid runner in both the morning and afternoon sessions, only beaten at the end of the day by Lando Norris' fast run onboard his C5-shod - and likely very light - McLaren.
"We just try to focus on ourselves and go through the programme we have, and so far it's been good," said Gasly who admitted that his team had yet to push its performance to the next level.
"We managed to do all the plan, a lot of laps, which is good for the engine and also the car.
"We know we have some good potential but we don't know what the others are doing at the moment.
"We just try to improve in the areas where we think we struggle a bit. I think we have a rough idea. We just need to keep our head down and work. It's going to be tight.
"We're just trying to push a bit more day after day. But still we haven't pushed flat out."
Gasly underlined Red Bull's progress since the start of pre-season testing and its strategy of incrementally dialing in the performance of its RB15.
"It was a really productive week last week and then to start the second week with that number of laps is clearly positive. But at the end of the day we just need to work," he added.
"Melbourne is coming pretty fast, we still have three more days of testing and hopefully we can learn a bit more about our package and extract more performance in the coming days.
"I believe we still have some [engine performance] left... I think we're just trying to push slightly more every day.
"We still have three more days of testing and I think we'll see more performance coming. At the moment we're just trying to put more mileage on the car and learn more about the package, but so far we're pretty happy."
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