Manager David Moyes is set to offer £27 million to test Chelsea's resolve with United looking to address their problems on the pitch which have seen them fail to keep pace in the title race.
Mourinho has targeted Rooney as the striker he wants to lead his new-look Chelsea team with his current crop of forwards failing to score the goals.
Last week, United manager Moyes admitted that the striker's future could be in the balance if United fail to qualify for the Champions League, as reported by the Daily Mail's Chris Wheeler.
Despite claiming that Chelsea won't be buying a striker this month, as the Daily Mirror's David Anderson reported, if Mata were to go to United, Mourinho would look to Rooney to fill the void.
The deal could work for both teams. United are looking for a creative spark like Mata in midfield, and Chelsea are seeking a striker talent like Rooney.
The England striker has nine goals in 17 Premier League games, ESPN stats show, but niggling injuries have kept him out of periods of the season.
His goals would spearhead Chelsea's title challenge.
For United, the signing of Mata would be vital. The Spaniard won the club’s player of the year award for the past two seasons and was named in the PFA team of the year for 2012/13. He was instrumental in the team's Champions League victory under Roberto Di Matteo and was influential in caretaker coach Rafa Benitez's success last year.
Mata’s frustrations at being a fringe player in Jose Mourinho's Chelsea have been publicly aired. When substituted during the recent win at Southampton, he showed his clear frustrations at the decision.
The player has been linked with a host of clubs, including Paris St. Germain, whom Jeremy Wilson of the Telegraph says will likely make a bid this January.
Mourinho made it clear that Juan Mata did not fit into his current Chelsea team. For the first time in the New Year, he opened the door for his departure, per the Daily Mail Online’s Neil Ashton.
I don’t want him to go, that is my opinion and that is my wish - but my door is open. The club door is open too, so when a player wants to speak with us we are there waiting for them. But if you ask me do I want to sell him, I don’t want to.
However, a potential move to Manchester United in January—hinted at by Paul Handler of the Manchester Evening News—would likely reignite the flair we associate with the Spaniard, who knows his chances of being selected for Spain’s World Cup squad this summer are under threat.
United are lacking real flair and creativity this season, but Mata is the kind of player who would help the Red Devils push for a place in the top four.
United have created significantly fewer chances then any of their rivals as stats collated by Squawka show, a problem Juan Mata could fix.