#4 Ousmane Dembele (Barcelona)

There were question marks over Barcelona's decision to replace Neymar with teenager Ousmane Dembele last summer. Neymar was an established player and one among the best in the world while Dembele is still a work in progress.
Dembele enjoyed an incredible 2016-17 season with Borussia Dortmund as he scored 10 goals and racked up 21 assists in 49 games for the German club. His incredible form earned him a call-up to the French national team and also to Barcelona who were desperate to replace Neymar, coughing up in excess of £100 million to land him.
But, Dembele has underwhelmed all season and perhaps it was too big a stage for the 20-year-old. He also suffered a thigh injury that kept him out of the game for more than three months which further derailed his progress.
He has not been able to replicate the form he exhibited at Dortmund and has played only 19 games in all competitions, scoring just twice. Also, Ernesto Valverde has been reluctant to start him regularly and this may have dampened his confidence as well.
He still has his career in front of him and there is no question about the talent he boasts. Sometimes, certain players need a bit of spark from somewhere and with Dembele, it is just a matter of time.