#4 Ousmane Dembele

You know you're in for a tough challenge when you're made the most expensive player in a mega club's history and signed primarily to replace one of the best players in the world when you had just turned 20.
This was the exact scenario Ousmane Dembele found himself in and if the pressure was not enough already, a serious injury barely a month into his arrival further hampered issues and ensured that his first season was not one to remember.
The Frenchman, however, capped the 2017/2018 season with a World Cup triumph in Russia and despite starting his second campaign at Barcelona brightly, injuries once ore robbed him of taking a part in the crucial end of season run-in, while he also faced accusations of disciplinary and fitness issues.
The result of this is that despite impressing on occasion, the French international has not done enough to prove his worth to Barcelona two years on from his arrival and with the imminent arrival of Antoine Griezmann, Dembele might have to leave Spain in search of regular football somewhere else.