4) Lionel Messi -> Ousmane Dembele/ Carles Alena
The greatest player in club history is also the toughest to forget about. After his debut in 2004, La Pulga has established himself as one of the greatest players to ever grace the game. Although he has a few seasons left in his contracts, Barcelona has to be prepared for life once he hangs up his boots.
Two names come above others when thinking about the next no. 10.
The first one is Ousmane Dembele. The Frenchman was brought in summer of 2017 to replace Neymar. During the first season, Dembele was plagued with injuries which halted his progress, and in the later part of the season, he showed the glimpse of his generational talent but was still not able to justify his market value.
But since the start of 2018-19 season, the fans are witnessing a completely different Dembele. Scoring goals and taking on defenders has almost become a routine. In the meantime, he succeeded in impressing Valverde and earned his place in the starting lineup.
The second one is Carles Alena. Barcelona's famed youth academy's product is the youngest addition to the first side, handling the jersey no. 21. The first and most noticeable thing about him is how similar he is to Messi in terms of playing style and intelligence.
He further strengthens his candidacy after his impressive performance against Levante in the first leg of the round of 16 of Copa del Rey. Although it is difficult for him to start regularly for the first team right now due to the fact that the squad is currently packed in the midfield; but in future, there is a good chance that he will be a major presence in the lineup.