Matteo is a decent aggressive, defensive and tough Full-Back, with significantly limited on-the-ball and creative abilities, as well as attacking drive.
He is not the best man-marker in defending, and not even the cleanest of tacklers, but his tackling is brave, tough and in the majority of cases, effective, and this is one of his biggest assets, in my opinion. Defence is fine as it currently stands, but his Attack value should definitely be lowered to 70 (-3).
As I have already mentioned above, his on-the-ball technical skills are really limited. His Dribble Accuracy and Short-Passing are fine as they currently stand, but his Ball Control is definitely below the 80s, more like 77(-3), a bit higher than his Dribbling stats. Also, I see no reason what so ever to have him at a so high Teamwork value. Based on the above, I would lower his Teamwork to about 77 (-5), to limit his involvement and influence in the attacking build-up of the team.
On the other hand, his Long-Passing, in regards to long-balls being played forward, and over-the-top long-passes, is pretty good and his biggest asset going forward in my opinion, and it reminds me a bit of Leicester's Albrighton ability to play over-the-top long-passes to the likes of Vardy and Mahrez in the counter-attack. Having said that, his Crossing ability looks mediocre at best, in my opinion. His Crosses have just decent pace on them, and no spectacular accuracy on them. I don't know how to replicate good Long-Passing, but average Crossing ability. Maybe, by keeping his Long-Passing stats as they currently are, but lower his Swerve to 66 (-6)?
About, his Speed Stats, well, he has really good Sprinting Speed, but other than that he is really average. Not clever at all to have Response at 80s, and he is relatively slow for his position in moving with the ball, turning and dribbling-past opponents. Something like: Response: 78 (-4), Explosive Power: 76 (-3), and Dribble Speed: 76 (-2).
Darmian has good fitness levels and he is a relatively mobile player, but his current Stamina value is too much. Stamina: 85 (-3), seems fine for him.
The Box-to-Box and Offensive Sideback cards should be removed in my opinion, as he hasn't showed that he is worthy of these cards, more than players like Luke Shaw and Guilhermo Varela would be, and similarly his Aggression should also be lowered to be at best 80 (-4), and also his Attack Awareness should be lowered to 2 (-1), to make him less of an attacking-threat, making less attacking runs. Whether his Defensive Awareness should also be lowered accordingly, is debatable.
Moreover, his Form should definitely be lowered to 4 (-3) or 5 (-2), according to this Season's performances for Manchester United. Matteo started the Season so well in the Pre-Season Friendlies and in the first few Official Matches, but then the level of his performances fell so much, having also suffered some injuries, resulting to him losing his starting spot to the likes of Ashley Young and Guilhermo Varela, only to re-claim his starting-spot recently with some improved performances, and sharing it with Antonio Valencia, and then to be injured again in the last Weekend and possibly missing the Euros.
Finally, I really believe that he is stronger than this. As I have already mentioned, he is an aggressive, tough and strong Full-Back, in relation to his size, and rarely losing 1v1 physical battles. His Body Balance, in my opinion, should be raised to 82 (+1) or 83 (+2). Adding to that, although not using it very often, his Left-Foot is more accurate than average, and I would go for Weak Foot Accuracy: 5 (+1).