The Spain international has insisted that the tie is not over just yet, while Jordi Alba feels they should have scored another goal in the first leg
A Busquets strike in the opening 45 minutes followed by a Zubikarai own goal after the break helped Barca to a vital victory in the first-leg of the semi-final encounter, but the holding midfielder has insisted the Catalans are not there just yet.
"A 2-0 win at home is a good result. It was important not to concede at Camp Nou," Busquets told reporters.
"We now have to play the second leg at Anoeta, which is a difficult stadium. The tie is far from over. Hopefully we can replicate this performance in the return and make it to the final."
Jordi Alba, meanwhile, was pleased with Wednesday's win as well, but felt Barcelona could have scored another goal to effectively decide the tie.
"The 2-0 is a good result, but at home playing against a 10-man team, another goal would have been good to have.
"The team gave it their all and we have to do our best to win the second leg. I think we played a good game."
The return is scheduled to take place on February 12.