How do you solve a problem like Kagawa?
But as well as Kagawa played against Real Sociedad this week, it raised more questions for Moyes than it answered.
His talent was there for everyone to see. But that was never in doubt. It was obvious at Borussia Dortmund and, in splashes, at United last season.
The issue is his role in the team.
Against Real Sociedad, he started on the left of midfield, the position he's found himself in most often since moving to United from the Bundesliga in 2012.
At times when he's played there he's looked so bound by his defensive duties that he's been unable to create anything.
Not this time. With Antonio Valencia staying in his channel on the right and Ryan Giggs happy to shift across from central midfield, the Japanese midfielder had the confidence to roam wherever he wanted.
He popped up in the hole behind Wayne Rooney and Javier Hernandez. Then on the right, bouncing passes to Valencia and Rafael.
But as well as he played on the left, it was nothing compared to his performance when he finally got to play as a recognised No. 10.
When Hernandez was replaced with Ashley Young with 10 minutes to go, Kagawa was moved inside to play behind Rooney.
Had Robin van Persie—not in the squad against Real Sociedad—not suddenly become available last summer, it's maybe what Sir Alex Ferguson had planned all along.
But Van Persie was available, which leaves Moyes scratching his head for ways to fit all three into the same team.
The new United manager hasn't shown himself to be so adventurous that he would play them all as a fluid front three. He still seems married to the 4-4-2, or at least a variation of it.
That leaves one of the three out in the cold, or Kagawa on the left wing.
The positive for Moyes on Wednesday was that Kagawa proved he can play there and still be dangerous.
It's not ideal given that his movement, touch and awareness make him better suited to playing centrally. But it's better than being sat on the bench.
It should be remembered that Moyes is still getting used to his players. The process of getting to know what they can and can't do is a long one.
This week Kagawa gave him a timely reminder of his qualities, just when it looked like Adnan Januzaj might knock him further down the pecking order.
But it was another reminder of the problem Moyes faces. How do you fit three into two?