Chelsea Transfer News: Kalidou Koulibaly, Emanuel Mammana, Latest Blues Rumours

Chelsea are reportedly preparing to bring in defensive reinforcements over the summer and are eyeing both Napoli's Kalidou Koulibaly and River Plate's Emanuel Mammana to bolster their centre-back options.

According to Sky (via Salvatore Boemi on TransferMarketWeb), incoming Blues boss Antonio Conte is an admirer of Senegalese Koulibaly, while Mammana is also a Chelsea target despite John Terry recently signing a one-year extension at Stamford Bridge.

Koulibaly, 24, has impressed for Napoli since he moved to the Serie A club from Genk in 2014, and he played 33 Italian top-flight games in the 2015-16 season as they finished second with the second-best defensive record in the league, per WhoScored.com.

His profile has risen of late, and he has been tipped as a potential replacement for Mats Hummels at Borussia Dortmund, an indication of just how highly he is rated, per football analyst Tom Payne:

Given how far Chelsea have fallen in the past 12 months—from Premier League champions to a 10th-place finish—they need a major squad overhaul in the summer.

Most pressingly, they need to tighten up again at the back, having conceded 53 goals in the 2015-16 Premier League campaign.

Terry is ageing, and Gary Cahill remains unreliable, thus Conte will want to add further quality to the back line when he arrives, and Koulibaly is seemingly a key target.

Argentinian Mammana, 20, is another option, and he has also been linked with Napoli and AC Milan, while he recently admitted he would "love" to play overseas, per La Pagina Millonaria (via Calciomercato's Lorenzo Bettoni):

"

I am only focused on River Plate at the moment. Of course I’d love to play abroad, but the only thing I am thinking about right now is playing for River. That’s my second home. I’ve always believed in this club and playing here is the best thing that could ever happen to me.

"

Valerio Pennicino/Getty Images

Elsewhere, Chelsea reportedly have a "verbal agreement" in place to sign Juventus midfielder Kwadwo Asamoah, with the 27-year-old Ghanaian keen to join the Blues, per CalcioMercatoWeb (the Daily Star's Luke Gardener). 

According to Gazzetta dello Sport (via Gardener), Chelsea owner Roman Abramovich is open to spending "up to £20 million" to sign Asamoah, who joined Juve under Conte in 2012.

He has since won four consecutive Serie A titles and would add experience and versatility to the Chelsea side—he can play on the left flank and in the middle—which could be very useful as Conte looks to carry out an effective rebuild.