#2 Diego Costa
In the same summer of 2013, Liverpool tried to sign Atletico Madrid striker Diego Costa. In order to make up for missing out on Mkhitaryan, the Reds triggered Costa's £21.8 million release clause.
There were expectations that the deal would be completed soon given the release clause was met. However, Costa chose to sign a new contract with Atletico Madrid and signed for Liverpool's rivals Chelsea the next summer.
In a recently released biography, "Diego Costa: The Art of War", by Fran Gillen, there is a mention as to why Costa turned down Liverpool. The reason turned out to be Chelsea's then manager Jose Mourinho.
As per the book, Mourinho convinced the striker and Atletico to wait for 12 months, clarifying that Chelsea would pay more to secure his services later on. Eventually, this convinced the Brazilian-born attacker to stay put at Atletico for another season, following which he moved to Chelsea, winning two titles with them.
As he gets ready to return to Atletico, it is a case of another potential top player missed out under FSG.