Barcelona were already without defenders Gerard Pique and Jordi Alba, striker Neymar and goalkeeper Victor Valdes.
Barcelona's defeat in the King's Cup final means La Liga is their only chance of major silverware and a win against Bilbao on Sunday would almost end their title hopes.
Barcelona will be without Neymar and Jordi Alba for the final month of the season after both were injured during the Copa del Rey final loss to Real Madrid.
A week ago, Barca were well placed to repeat their record treble of La Liga, Champions League and King's Cup from 2008-09 but are now likely to end the season trophyless.
Bale's late goal sealed Real's 19th Copa title in a thrilling win as the Welshman filled the void left by the injured Cristiano Ronaldo.
Wednesday's match features two teams whose focus is on attack and it should be an open, entertaining spectacle between the world's two richest clubs by income.
Ronaldo will miss Wednesday's King's Cup final against Barcelona after failing to recover from knee and thigh muscle problems.
Real and Barcelona meet King's Cup final in Valencia in the latest edition of the 'Clasico' between the world's two richest clubs by income.
The current Barcelona squad have a great deal left to give and there is no need for a sweeping overhaul in the close season, captain Puyol said.
Barcelona's season is threatening to implode with Wednesday's King's Cup final against Real Madrid looming after a nightmarish week.
Barcelona compounded their exit from the Champions League by losing 1-0 at Granada, letting Real move ahead into second place with a 4-0 win over Almeria.