Athletic Club is a great team and they will want to beat Barcelona at the end of this season. Barcelona have already secured their trophy in La Liga and they will want to continue their winning streak. Accordingly, they may not field a team with second-tier players. I think Barca will play with their full strength and will try to beat Athletic Club. We can say for sure that it will be an exciting match between both the teams and Barca will have a higher chance of winning. Although Barca is ahead in the win statistics of these two teams the win or loss depends on the best performance on the specific day to get the win.
Bilbao is indeed a great team and of course cannot be underestimated and of course in their last 3 matches they have always won when competing and the last one against Valencia won with a score of 0-1 and of course at the end of this match Bilbao will definitely want to finish their last match with a win so yes in my opinion it will definitely be an exciting and tense match. Barcelona must also have the ambition to win because they definitely want to show their best performance at the end of this season in La Liga.
of course we don't know whether Flick will field second-tier players or not but what is clear is that in that match both teams will be ambitious to win if in my opinion second-tier players will be fielded as well as first-tier so according to my prediction Flick will definitely try players who have rarely played so far. but what is clear in my opinion in that match it will be difficult for those who will bet because as usual at the end of the season it is always full of surprises. but if I am more in favor of Barcelona to win.