Team owner Dietrich Mateschitz does not think Red Bull can mount a serious championship challenge in 2015.
The Austrian billionaire made an ultra-rare paddock visit this week at the opening test of the pre-season.
After Jerez, Mateschitz said: “Mercedes is again out of reach.
“I think if we are able to reduce the gap, that would be good,” he is quoted by Speed Week.
Mateschitz also witnessed works partner Renault stumble at Jerez with a reliability problem for its uprated turbo V6, but noted: “If they manage to reduce the horse power deficit by 40 or 50, we will be in an area where, with a good car, we can put pressure on Mercedes.”