Moyes had enough on his own plate to deal with after the defeat: It was the first time United had lost to Newcastle at home since 1972, and the result leaves them firmly in mid-table.
But in quotes given to the official Manchester United website, Moyes explained the bizarre circumstances behind Kagawa's absence:
Shinji was very sick after the [Everton] game and he did a bit of training on Friday but he was low. All of the stats that we look at were low so we felt we had better not take a risk in case we got an injury by playing him. ...
It was a bad sickness. He thinks he ate too much, and he had to get his stomach pumped, but I think he is okay.
Kagawa may not have been up to playing, but he was at least up to taking his place in the dugout to watch the encounter live.
The man he was sitting beside in the dugout, Marouane Fellaini, was also the subject of Twitter talk during the game.
In the Belgian's case, however, it was because he was snapped looking at his phone while the match was taking place.
United are ninth in the league with 22 points from their first 14 games.