Chelsea have beaten Barcelona and AC Milan to the Argentine international defender Nicolas Otamendi, reports Daily Express.
Both AC Milan and Barcelona tried to sign the Porto player in the summer but failed to agree a fee for the 25-year-old.
Although the Portuguese champions are reluctant to let him go, they are resigned to losing him next summer and believe the player is bound for Stamford Bridge.
Mourinho is seeking reinforcements at centre-back as he currently only has John Terry, Gary Cahill and David Luiz as permanent options for the position.
Otamendi, who has 15 caps for Argentina, was called up by Diego Maradona in 2009 after making just 11 professional appearances for previous club Velez Sarsfield.
Barcelona meanwhile have been looking for defensive reinforcements all summer with Chelsea's David Luiz also targeted by the Nou Cap outfit in the summer.
Barcelona reportedly offered £34.5m bid to the Blues for Luiz, which was flatly rejected by Mourinho.
Reports that Otamendi will move to Chelsea may provide a boost in Barcelona's pursuit for the Brazilian however, as Mourinho is yet to be convinced by Luiz's credentials as a centre-back, having played just twice in the Premier League this season.