Neymar spent four years at Camp Nou until 2017, when he left for Paris Saint-Germain as the most expensive player of all time in a €222million move.
While the Brazilian has undoubtedly caught the eye in Paris, scoring 47 goals and setting up another 26 in just 52 Ligue 1 matches, rarely has he appeared happy.
A return to Spain with Barca or Real Madrid has often been mooted, though reports linking him with his former club have been significantly more prominent in the past year.
Del Bosque, a Madrid icon and World Cup-winning coach with Spain, thinks he is a problem and cautioned the Barca hierarchy against caving into the supposed demands of players who reportedly want Neymar back in Catalonia.
"It is the clubs that must decide who to sign and who not to sign," Del Bosque said.
"You should not pay attention to what the players say, for that there are sports directors and technical secretaries. It is very difficult for a footballer to speak ill of another footballer who has been his team-mate. I don't remember almost anyone who has.
"[Neymar] is a difficult boy. For me he is not a good example, and for the record, for me he is great as a player.
"If you ask me to tell you the top five in the world, he is safely on my list, but on the pitch he tries to cheat, he simulates a lot. And also, how did he leave Barcelona?"