Watching him I feel it's pretty obvious that he completely lacks confidence right now and doesn't commit to anything, which makes things actually worse. That bouncing ball, the Maguire that came here wouldn't have hesitated and just headed it forward. The Maguire we have now hesitates, notices there is another player around him, loses sight of the ball gets in the wrong position, ball bounces over him and the striker would have been through on goal if Bailly hadn't covered for him.
There are other incidents where he drops awfully deep and can't close the gap in time anymore. Same with the goal, he is so desperate to fall off and not commit that there is enough space for his opponent to simply shoot.
Somebody needs to find a way to get some aggressiveness and confidence back into him. Hire Ibra back as his motivational coach or something, he needs some of his attitude.