5 Reasons Why Chelsea Should Have Kept Romelu Lukaku

5. An Unproven Costa

Last season, Diego Costa was a snarling, brutish and menacing beast, but he was also one of the most feared strikers on the continent. Following Columbian talisman Falcao€™s move across the Atlantic to the tax-haven of Monaco, Costa became the focal point of the Athletico attack, and flourished, notching 36 goals in 52 games. One of three current Chelsea players who departed the Stamford Bridge turf an Athletico victor last April, it wasn€™t much of a surprise to see Abramovich part with £32 million to lure the Spanish hotshot. However, it must be noted that last season might well have been a fluke. Costa is 25 years old, and last season was the first time in his career that he has scored more than 10 league goals. Just two years ago, he wasn€™t even deemed worthy of the Athletico starting XI and had been farmed out to Rayo Vallecano on loan. There have been occasions where strikers enter a purple patch in their career €“ a rich, yet brief, vein of goalscoring, only to resort back to form within a number of months. It is mentioned with a hush around the parts of West London this summer, but the Stamford Bridge faithful surely won't forget the fabled 'striker curse' that consistently plagues the club. After all, they are served a constant reminder in the shape of profligate £50 million man Fernando Torres on a weekly basis. Should Costa€™s golden touch wear off sometime in October, Mourinho could be left with yet another expensive dud, and wishing he still possessed amongst his ranks the boy with the proven Premier League track record.