I've said this for sometime and repeated it on the match day thread:
He doesn't make saves, he makes blocks. Shots have to hit him.
His footwork is a joke for a professional keeper, always late, leaden footed, is still setting himself as shots come in, leaving him with distances to cover. Example; Hughes had a volley from the edge of the area, it's in the middle of the goal but Onana is at finger tips to make what is a routine catch tbh.
I've said it so many times in here but his hand eye coordination and technique in actually handling shots and ball manipulation is absolutely insane, I've never seen anything like it. It's why you see so many shots come off of him at weird, unpredictable angles, seemingly always back into danger.
The ball always hits the base of his hand/top of his wrist, like a block, sending the ball back where it comes.
He cannot judge the flight of the ball so saves rarely hit the "meat" of his palm and fingers, instead hit his wrist where, and this is crucial, he has not control.
He had no athletic ability, no spring, slow to get down, cannot cover the top corners, cannot cover the bottom corners, really does play like a 5'8" keeper.
So much technically wrong with him but everything was overlooked because he can pass the ball (so what tbh) and he's ETH guy.