The 29-year-old has long been on Antonio Conte’s wish list, having failed in an effort to sign him last summer, and remains a top target.
But Sky Sports report that Jose Mourinho is keen to trump Chelsea to the Belgian’s signature and have begun ramping up their charm offensive.
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A deal has yet to be agreed, however, with Roma notably tough negotiators – Chelsea had a final bid believed to be around £34 million rejected last year.
Conte is known to be a huge fan of Nainggolan and was expected to reignite his pursuit of the midfielder when the transfer window reopens.
The Italian coach even spoke to the former Cagliari man about a move to Stamford Bridge.
‘Yes I talked to him,’ Nainggolan revealed in March. ‘They were really interested and wanted me over there. That’s all I can say.’
Chelsea need to expand their squad ahead of their return to European competition next season, with Conte expected to add several new faces.
Nainggolan has been in excellent form for Roma once again this season, scoring 11 goal in Serie A, though the club look set to just fall short of the title.
Mourinho, meanwhile, is known to want to expand his midfield options, especially if Michael Carrick does not sign a new contract.