A large, aggressive, quick, and physically strong yet elegant player, Koulibaly is recognised for his aerial prowess, anticipation, positioning, tackling, character, technique, and passing ability as a defender. He has also been praised by pundits for his overall solidity as a player, and his ability to make interceptions; however, he has also drawn criticism for giving away too many fouls. Due to his versatility, he can play both in his usual role as a central defender, or as a full back on either the right or left flank, in both a three or four-man defence; he has even been deployed as a defensive midfielder. During his time at Napoli, his ability to play the ball out from the back saw him function as a ball-playing centre-back in manager Maurizio Sarri’s attacking, possession based-system. Currently considered to be one of the best and most complete defenders in world football in the media, his ability, playing style, tall stature, and imposing physique have earned him the nicknames “K2” and The Wall from his fans.