Kalidou Koulibaly has been a force for Napoli this season. He's been a near-constant presence on the back line, and rarely puts in less than a high-quality shift, frequently finishing matches as the standout performer in defense.
When he first arrived, though, he was an unknown. A mystery. No one knew who he was, and almost everyone doubted that he was any good. Sure he was big, but how could some random French scrub from a second-rate Belgian team be of any use to Napoli in Serie A?
Obviously that hasn't turned out to be the case. According to Koulibaly, the person responsible for unlocking what he can do and helping prove to the fans that he's far more than just "useful" is none other than Rafa Benitez.
"When I arrived in Italy, nobody knew me and they were doubting my skills. Then I rolled up my sleeves and I’m happy now, I’m improving game after game.
"I didn’t expect the call from Napoli, I couldn’t believe in it when Benitez called me. Rafa is a great Coach, it was an amazing thing. He told me that he was interested in me and wanted me on his team, then I joined Napoli and I have to say that he helped me a lot, he knows what I need."
-Source: Canal Plus TV via gianlucadimarzio.com
No matter what else happens to Rafa during his time at Napoli, if Koulibaly continues down the developmental path he's on, he will have done Napoli a great favor by tapping the Frenchman's potential. Koulibaly doesn't just have a chance to become one of the best defenders in Italy, he could become one of the best in the world. It's going to be difficult for Napoli to hold on to him in the long run as some giant clubs will come a-knockin', but if they manage the feat it will be well worth the effort.