#3 Jack Wilshere
Everybody already knows about Jack Wilshere's descent from a key player at Arsenal to a bench-warmer for West Ham, and the main reason behind his fall has been due to injuries. Constant setbacks have been a theme throughout Wilshere's career and it doesn't seem like an issue that's going to go away any time soon.
Mocked for being "made of glass" during his last few years at Arsenal, Wilshere was loaned out to Bournemouth in 2016 and showed a fair bit of promise, but once again, injury struck and he was sidelined for several weeks. He returned to Arsenal with the knowledge that he was probably going to be sold.
And he was - to West Ham last summer, on a free transfer. He has only played five matches for the Hammers this season and is currently sidelined with an ankle injury (surprise). It's safe to say that Wilshere's days of being a key player at a top club are over, along with the chances of him getting into the England squad, especially with some of the talent in there right now.