#5 A second defensive midfielder
Before you get me wrong, the pivot needed would be the second choice after the brilliant Busquets. Right now, there isn't a player matching Sergio's style at Barcelona to ensure the flow of play remains the same whenever the Spaniard is absent; luckily, Barcelona managed to reach mid-way through the season avoiding an injury to the La Masia graduate.
When it happens, however, Valverde's whole plan will take a hit and probably be scrapped altogether, since Busquets provides an unmatched layer to Barca's style of play.
The pivot needed should be calm on the ball, tactically intelligent, and defensively strong to protect the back four. Tough qualities to find at a low price in the transfer market, which gives reason to search within the academy, I am sure that somewhere among the youth ranks lies a player who has Barcelona' DNA enabling him to fit in seamlessly with the main squad. It is definitely a risky option to take, but without risks we wouldn't have seen Busquets playing right now.