Athletic must overturn a 2-1 deficit against Sporting in Bilbao on Thursday if they are to progress to their first European final in 35 years.

Midfielder Javi Martinez is set to return from suspension for the hosts while forward Iker Muniain is available after recovering from eye inflammation.

"There isn't any situation in the alternatives presented by the game that we aren't prepared for," Bielsa said.

"By alternatives I mean to attack correctly and defend so we don't concede goals that can complicate the match like extra time or penalties.

"We are prepared for all of these situations and we just have to try to overcome any of these adversities. There isn't anything in particular we aren't prepared for.

"It is true that the best team doesn't always win but it's true that the best way to get there is to try to be the better team on the pitch."

Emiliano Insua and Diego Capel scored four minutes apart to clinch a come-from-behind victory for Sporting in the first leg.

Athletic midfielder Andoni Iraola is expecting more pressure from the visitors' forwards in the return fixture.

"Sporting has dangerous players like Diego or (Andre) Carrillo," Iraola said.

"They are not afraid of attacking, they give depth to the team and play very well at counter attacking. We'll have to be very concentrated the whole match.

"We obviously are against a very competitive squad that is going to make it very difficult for us but if we want to play in Bucharest we know what we have to do."

Athletic reached the final of the UEFA Cup in 1977, losing on away goals to Italian giants Juventus.

Should they overcome Lisbon, Athletic will face either Atletico Madrid or Valencia in an all-Spanish decider in Bucharest on May 9.