2. Neven Suboti & Mats Hummels (Borussia Dortmund)
Serbian regular Suboti and German international Hummels have been nothing short of immense as of late, and the defensive pair have made a massive contribution in Borussia Dortmund's rise to Champions League-and-Bundesliga contenders. Subotic contributes the physical prowess of the pairing, whilst Hummels has more of a technical, intelligent way to his game. The pair compliment each other and this has led to them being one of the finest European centre back duos in football today. As a result, both have been heavily linked with some of Europe's best clubs and it is in Klopp's best interests to hold onto two of their best players unless and excessive sum of money is exchanged. The scariest thing about this pair is that they are both just 24 years of age, and the idea that they have many years left to improve is a mind-boggling thought for any football fan who knows the talent they both already possess. Suboti is a shoo-in for Serbian captaincy in the future, and Hummels is a top candidate for Germany once Philipp Lahm retires. If Klopp can hang onto both of them, - as well as the likes of Reus, Gündoan and Baszczykowski - Champions League success is surely imminent. Expect to see numerous bids made by the likes of Barcelona and Real Madrid in the future. Imagine Varane paired with either Suboti or Hummels? That's a horrifying thought for any top striker.