Red Bull team principal Christian Horner fears a Ferrari resurgence, despite seeing his drivers clinch a one-two at the Turkish Grand Prix.
Sebastien Vettel was an untroubled winner but Mark Webber had to battle with Ferrari's Fernando Alonso before finally securing second place.
"You can never underestimate the opposition," said Horner. "Ferrari are back and they pushed us very hard.
"They are very soft on their tyres and they make them go a long way."
For Alonso and Ferrari, it was their first podium finish of the season and confirmed they are back among the contenders after a difficult start to the year.
Spaniard Alonso fought a thrilling duel with Webber and overtook the Australian on lap 29 to move into second place. But 21 laps later, Webber returned the favour to secure the runners-up spot.
The racing between the pair clearly made an impact on Horner, who feels Ferrari have joined McLaren - victors in China last time out courtesy of Lewis Hamilton - as a threat to Red Bull's dominance.
And with Mercedes grabbing fifth place through Nico Rosberg - and displaying good pace throughout the weekend - Horner is far from feeling complacent.
"McLaren have looked very, very strong in the last couple of races - although they weren't as strong today," added Horner. "And Mercedes looked very fast yesterday [in Saturday's qualifying].
"I think things are going to change, there is a long way to go in this championship and it is important that we capitalise on days like today.
"It was a really sweet result today, especially after the problems that we had last year [when Vettel and Webber crashed into each other].
"To come back and have a really dominant race with Sebastian and a fantastic race with Mark was great.
"It was very strategic, plenty of pit stops, a real team race today, the guys in the pit lane were phenomenal and it was really rewarding to get a one-two."
Vettel's win extended his lead in the drivers' championship to 34 points from Hamilton, with Webber in third and McLaren's Button in fourth. Ferrari's pair of Alonso and Felipe Massa occupy the next two spots.
But world champion Vettel also sounded a note of caution despite his blistering start to the defence of his title.
"Judging on what we have done so far we can be very happy but we do not know what will come up next," said the 23-year-old German.
"We have to carry on doing what we are doing and get the maximum out of the car. There will be days when we get beaten but it is about minimising the loss."