Of course Memphis lacks confidence, he's been utter **** for nearly a year now. But his first 2 months were nothing to parade about either. He wasn't god **** awful, that's the extent of praise I can give for his United start.
Plus like it's been discussed before, where is Memphis supposed to play exactly? Martial on the left is unmovable, and between United and Monaco he had no issue playing well over 50 games last year. On the right Memphis is about as useful as a training cone hanging from a hot air baloon. Upfront he'd be a distant 5th choice behind Ibra, Rashford, Rooney and Wilson.
That doesn't leave much options for him I'm afraid.