Second season syndrome for Salah?

Michu

Swansea City v Queens Park Rangers - Premier League

Swansea signed the relatively unknown Michu from Rayo Vallecano in 2012, and he proceeded to make a mockery of his £2m price tag, scoring 2 goals and assisting 1 more on his debut, before going on to net a total of 18 times in the league. He would score 3 more in the League Cup as Swansea claimed the first major trophy of their 101-year history.

The next season he would only manage a paltry 2 goals in the league, a remarkable drop-off, and was loaned out unsuccessfully to Napoli before signing with an amateur team in Spain (for whom he is now Director of Football). A meteoric rise followed by a meteoric fall.