I'll give him the benefit info the doubt and say the keeper put him off, rather than he bottled it.
Overall though, I don't think he is quite good enough to play regularly at this level. It isn't because of that one miss that we will likely go down, but a consequence of our lacking quality in crucial positions over the duration of the season.
We should have left ourselves with far better options than El Ghazi, Trezeguet and Jota (remember him?) if we wanted to frighten teams.
If our relegation is confirmed, he will probably do a job for us next season at that lower level, just as he did in helping to get us promoted in the first place.