"The maestro" is absolute magic in game for my squad. He has the perfect balance of pace, ball skills, and passing that make this card one of the best I've ever used. I completed his SBC for about 515k; an absolute bargain considering his trade-able 90ovr card goes for around 1mil on the open market. I use a "maestro" card on him; which in my opinion, enhances his best stats to an unstoppable level.
The hidden stat that must not be overlooked is his incredible strength of 84. In-game his strength feels closer to a 93-95 range; as he can hold up the ball with ease, as well as wrestle defenders off of his runs. My style of play needs a strong CAM who is an immovable force in the center; allowing for pacey strikers to get into the open pitch behind defenders. Costa's ball control, along with his pinpoint passing is a dangerous combination going forward. I use him behind Papu Gomez and Mertens; the three of which create a deadly attacking force.
Pace: His pace isn't mind-blowing fast; however, is more than adequate for the CAM position.
Physical: Incredible strength; shields the ball well and can shake defenders when trailed by the CBs/CDMs.
Passing: Pin-point passing; incredible through balls with accuracy and power.
Dribbling: I've never played with a card who holds the ball with such ease. His 4 star skill moves and 4 star weak foot play close to a 5 star level.
Shooting: Great long shots, free kick accuracy, and shot power.
His cons are very minor; however, I will share a couple of items to have a fair and balanced review.
Defending: His defending in my opinion is very poor. For myself this is a non-issue as I play a 4-3-1-2 with Costa as the CAM with the "Stay Forward" player instruction. For those who expect their CAM to drop to the deeper midfield and perform standing tackles to help win the ball back, you'll find that Costa's card is not built to perform in defending scenarios (although he will win headers with his strength when battling with these defenders).
Shooting: His finishing inside the box can be slightly off-color at times. He has missed a few open chances for me thus far; however, he almost always made up for these misses by making an incredible play the very next shot opportunity.