Both teams had their fair share of chances and posed a threat to each other especially the first 20 minutes and last minutes of this first half. Unfortunately, Atletico Bilbao lost a good left back defender Yuri to injury just in first minutes. But, they managed to maintain their defensive lines solid and even outperformed Barcelona by creating more opportunities. So in my opinion Barcelona was significantly affected by their absences, especially in midfield which appeared quite weak today and worse than usual which allowed Bilbao more chances if not for Ter Stegen's savings they would receive many goals.
If we don't see Xavi making tactical adjustments and strengthening the midfield, I would bet that Barcelona might concede at least one goal and probably lose the match today.
Barcelona performance is poor in the first half and if they don't wake up and change their game pattern, if they continue like this in the second half, they might lose to Athletics. I believe when David make some changes in the second half, they will be able to make chances to break the deadlock. The deadlock hasn't been broken yet and it is still 0-0.