Manchester United appear set to considerably test Chelsea's resolve with a large offer to sign Spanish midfielder Juan Mata.
According to the Daily Mirror, the Red Devils claim that they have not yet tabled an offer for the former Valencia playmaker - but it is believed that they are in the process of preparing a bid of £37 million to land the player.
25-year-old Mata joined Chelsea back in 2011 and established himself as the club's top performer and a firm fan's favourite during his subsequent two seasons at Stamford Bridge.
The 2013/14 campaign has been far more trying for Mata, however. Although he still appears to retain the usual backing from the stands, it seems as if he is not a favourite of returning manager Jose Mourinho.
With the Portuguese often preferring to deploy Oscar in that traditional 'no.10' role, Mata has found his role largely diminished at Chelsea - a fact that appears to be a source of immense frustration for the player given his rather childish reaction to being substituted during a Premier League clash away at Southampton earlier this month.
Manchester United, meanwhile, have endured a wretched season to date and appear to be lurching from one disappointment to another under the tutelage of David Moyes. While the Scot boats an impressive managerial pedigree from his lengthy spell with Everton, he seems to be finding it somewhat difficult to adequately fill the sizeable void left by the departure of iconic compatriot Sir Alex Ferguson.
Moyes and Manchester United were first linked with a potential move for Mata during the summer transfer window, but ultimately a deal obviously never materialised.
And although it very much appeared initially as if that saga was dead in the water after Moyes failed to land a number of his preferred transfer targets, such rumours have intensified once again in recent days with a mammoth bid now seemingly imminent.
At this stage, it seems unclear if Chelsea would be willing to allow one of their brightest talents to move to a direct title rival - but those aforementioned reports suggest that Mourinho is keen to keep hold of the player.