I am from Zagreb and i follow Dinamo and Marcelo every game. So lets start... His main position is Central midfielder, but he played Dm in his early days. He is developing to become a box to box midfielder, with diverse skills. With Croatia he mainly plays right now as defensive midfielder with Modric and Rakitic, benching even Kova! why? Well he is has better defensive capability then Kova and a team needs a player like him.
He can run all day, always among the best runners in most games. He can tackle solid but his is not a Pitbull like Medel. His style of play is totally box to box, even ih he plays on a deeper- def. midfield role. He joins attacks, and knows how to score (often up close, but knows how to score form range aswell)
Other advantages: he has above the average tehnique, can easily hold the ball, solid playmaker, can spread the ball and has a solid long ball. His style of play is ideal for footbal played in Italy, and therfore Inter aswell. In my picture he will be tryed in defensive midfield role like he plays for Croatia. I think that this is his future role.
Weakness: He is not a profund dribbler like Kova, but occasionally know how to get pass a player or two. On average 2 dribbles in match.Biggest weaknes is that he is not constant wiht his pass precision - especially long passes, but he has improved that recently.Also he is known to be not the smartest person off the pitch, so some poeple in Croatia maybe didnt like him at first - like me. but who cares.
So conclusion - Good buy for Inter. You will have a player that has a future in both defensive roles or central midfied playmaker role, that can score goals, has variety of skills, great young age, with lots of space to progress. He is a better option then Susic in my opinion. Brozovic is better at the moment.