#2 Gervinho
Many had touted Gervinho to become the next big thing when he joined Arsenal from Lille in 2011. Before joining the Gunners, Gervinho had scored 15 goals and had been a star player for the French club. However, he had a mixed debut season at the North London outfit and played mostly as a second fiddle in the subsequent season.
His declining game times then led Arsenal to sell him to AS Roma. Fortunately, his move to Roma was a success and became a turning point for his career. After two-and-a-half successful seasons at Serie A, Gervinho spent some time in the Chinese Super League before coming back to Italy in 2018.
Now the 31 years old is a star performer for the newly-promoted Parma. He has scored 9 goals this season, two of them are against Juventus in Serie A. Had Arsenal never let him left, the Gunners could have a much better winger than Iwobi.