Nico Rosberg has described the W01 as a "disaster", as Mercedes moves closer to abandoning development of its 2010 car.
The 25-year-old German again outqualified his famous teammate Michael Schumacher at Valencia, but his prize was a mere twelfth on the grid.
He then scored no points in the race, despite the Brackley based team - winners of the 2009 world championship as Brawn GP - using a raft of improvements in Spain, including a Red Bull-like blown rear exhaust layout.
Rosberg was angry immediately after the race, and a week later has told the Cologne publication Express: "It's a disaster."
"The problem with the tyres is well known to the team. For weeks we have said we are coming to the front, but nothing happens -- actually we go backwards."
Rosberg admits he is "angry" with the situation.
"If you're twelfth, behind both Williams - who two weeks ago were nowhere - what do you expect? I went from Williams to Mercedes because I thought I would have a winning car."
Boss Ross Brawn said the team will continue to work on the W01, but admitted the time will come for a new approach.
"We have not done a good enough job," admitted the Briton.
"First we need to get our new aero package working properly, and depending on the result we will decide to what extent we then concentrate on next season," added Brawn.
Source: Motorsport
