Senegal defender Kalidou Koulibaly from Napoli on a four-year contract, the Premier League club said on Saturday. British media reported that Chelsea paid a fee in the region of 32 million pounds ($37.93 million) for the 31-year-old, who becomes the London side's second summer signing after Raheem Sterling. "I'm very happy to be here with this team at Chelsea," Koulibaly said in a statement. "It's a big team in the world and my dream was always to play in the Premier League. "Chelsea came first to get me in 2016 but we didn't make it. Now when they came to me I accepted it because they really wanted me to come to the Premier League to play for them." Chelsea lost centre backs Antonio Rudiger and Andreas Christensen earlier in the close season, and Koulibaly's addition will come as a boost for Thomas Tuchel's side as they look to close the gap on Manchester City and Liverpool.