The quit threats from Red Bull owner Dietrich Mateschitz continue to grow louder with the Austrian saying he is losing his "will and motivation" to stay in Formula 1.
Having won four consecutive Drivers' and Constructors' Championships from 2010 to 2013, the Milton Keynes-based squad have found life a lot more difficult the past two seasons.
They finished a distant second to Mercedes last year as their power unit supplier Renault struggled to come to grips with the new V6 engine regulations while their chassis was also not up to scratch.
This year they have dropped even further behind and their billionaire owner Mateschitz has again threatened to leave F1 due to the regulations.
"What else has to happen that we will lose our motivation completely?" he told Red Bull's Speed Week magazine.
He added: "They take from us not only time and money, but also the will and motivation.
"There is no driver and no chassis which is able to compensate for this lack of horsepower."