For me he had four blunders yesterday. The first goal, obviously.
Then his placement here on the second. Not saying he should have saved it, but look how far he was from the ball. It could have been square down the middle of the goal and he still wouldn't have got a hand to it. From that angle, you have to cover more of the goal.
Then his handling of Ilaix's shot. Came straight at him and he parried it right at the feet of another Celta player, who luckily also hit it right at Szczesny.
Then punching Mingueza in the face, which could have been a penalty.
Didn't count any great saves. Maybe one, where he came out well and blocked a close finish by Borja.