Well, this ends any speculation of Momo leaving to go to Juventus or Barca. After weighing the positives and negatives, I'm leaning more to agreeing with this move. The positives are his youth, he's only 22 years old, and we've all seen how dominating he can be. He may not have had the best year this past campaign, marred by injury and inconsistency, but I still view him 'in development.' Furthermore, he's got a world class role model in Mascherano, who he might have to end up replacing after the end of next season.
The thing he needs to work on most, other than avoiding injury, is his passing efficiency. Too many times last year he would make a great tackle and then throw the ball away. Mascherano is a solid passer who knows he doesn't have to make the spectacular pass to be appreciated, which is probably why he is so great. Impatience on the ball and understanding one's role are two things that usually come with experience and hopefully, Momo will improve on these aspects in the future.
Also, if you wanna get a better look at Rafa's goatee, go here.