I don't think Saka has ever taken a competitive penalty in his career. He's only a teenager. Training doesn't get you ready to be the fifth of five in that kind of pressurised situation. He should never have been put in that position. It does no credit to the likes of Grealish and other more experienced players.
The whole game was odd, he started with 7 defensive minded players and all his skilled attackers were on the bench - - where they stayed until it was too late.