He had an adductor injury in 15/16 kept him out for 10 days or so. Reading the different type of strains, by the sounds of it, worse case he may have a strain grade 1, which is 'Grade 1 strains are a mild injury, where a few fibres are torn or disrupted but the muscle bundle is still intact.' Grade 1 can keep a footballer out upto 2 weeks.
Grade 2 affects ability to walk, he seemed ok enough when coming off and I think Di Maria was just pissed that he got injured on debut which is understandable for someone who's usually all well and fit.
Wouldn't be me without reading too much, so a risk of injurying adductors is usually down to the following: 'Risk factors include previous hip or groin injury, age, weak adductors, muscle fatigue, decreased range of motion, and inadequate stretching of the adductor muscle complex.'
Can't be age

, he seems professional enough to look after his own stretching. I'd say it's muscle fatigue. We're burning this guy already!