Sergio Aguero

Kun was signed for £38m from Atletico Madrid and quickly set about justifying that investment, with 2 goals and an assist on his debut despite only coming on in the 59th minute. He would go on to score 23 goals for the Citizens, including the most famous goal in the Premier League Era, the title-winning, Martin Tyler aneurysm-inducing goal against QPR.
He couldn't follow it up though, and struggled to a haul of just 12 goals. His is perhaps the quintessential example of second season syndrome, because he bounced right back with 17 in 23 the following year and hasn't scored less than 20 in a league campaign since. The perfect sophomore slump.
So what will happen to Liverpool's wing wizard? Will he be able to break the curse like Ruud Van Nistelrooy and Thierry Henry, or will he struggle, as the opposition finally work out how to deal with his trickery? We can only wait to find out