The Blaugrana are under fire from certain sections of the media for being one-dimensional after their failure to overcome Chelsea in the semi-finals of the Champions League
It has been suggested following the Blaugrana's semi-final exit at Camp Nou on Tuesday night that while the Catalans' famed 'Tiki-Taka' brand of football is easy on the eye, it cannot be relied upon to unlock every defence and that Pep Guardiola needs to vary his side's approach to the game.
However, Bielsa insists that Barca should not even consider abandoning their footballing philosophy.
"This idea of a 'Plan B' is not one I understand," the Argentine coach told reporters during a press conference on Wednesday.
"The game yesterday [at Camp Nou] indicates that attacking football has nuances. But styles cannot be changed.
"Even if the best team doesn't always win, the best way of winning is always by trying to be the best."
It has also been claimed that Blaugrana are now suffering from fatigue after nearly four years at the top, which would be good news for Athletic, who face Barca in the Copa del Rey final next month.
However, Bielsa is actually hoping that the reigning world champions are in peak physical condition when they collide at the Vicente Calderon.
"A tired Barcelona is obviously better for us," he confessed. "But I would prefer us to beat the best Barcelona."
Meanwhile, Athletic go into their Europa League semi-final second-leg clash with Sporting Lisbon at San Mames on Thursday trailing 2-1 after last week's visit to the Portuguese capital and Bielsa revealed that his primary focus is on striking the right balance between defence and offense.
"We must defend well so that they don't score, and attack in order to find the net ourselves," he admitted.
"But the best way of expressing ourselves is just by playing the football we always play."
Athletic's meeting with Sporting in Basque country gets under way at 21.05CET.