Ball retention massively helps, his stats are way off on Alonso btw as the poster above you has stated. Pressure and pressing is only one half of the game, Yaya rarely loses the ball because of his ability to keep it in tight spaces. Yaya's technical abilities could easily see him play the Alonso role, where he can trigger attacks, fill in an the back and shoot from range/push on when we need a goal. Its almost like having 3 centre backs on the pitch, pushing the full backs on to get involved in the attacks. Yaya is at his best when we have possession and we will dominate possession when Pep comes.