4) Thomas Vermaelen
Vermaelen’s Arsenal career has ground to an unfortunate halt. Still the club captain, Vermaelen enjoyed a wonderful debut season in 2009/10, where he established a reputation as one of the top flight’s finest central defenders. Since then though, injuries and low confidence have halted his career, and he’s been very much the third choice centre-half this term behind Per Mertesacker and Laurent Koscielny. As a result, he’ll likely leave to play regular first-team football.