He did the back pass because he doesn't have the skill to turn and look forward. So it's not a "simple mistake". It's a terrible piece of play because he's just not very good.
Better players spin with the ball.
He's literally been doing this for seasons now. Passing it in the direction he's facing as soon as it gets to him. Yet people keep on defending him. He has not the talent or skill to take a touch, draw a player, use agility to turn direction quickly, wiggle, shimmy, create an angle for a pass.
He ALWAYS passes it quickly to which ever direction he's facing as he receives it. That's a bad bad player creating his own mishaps.
Wasn't a mistake. It was his level in its full and ugly glory. But yeh, Call it a simple mistake and let's carry on watching him do the exact same sequence, only further up the pitch where instead it hampers our ability to create shots on goal.