The 28-year-old played under the Portuguese tactician when the latter was in charge at Stamford Bridge. Mourinho was sacked by the west London club in December 2015 and months later, he was appointed as the Red Devils manager.
According to the Manchester Evening News, Matic has discussed the possibility of playing under his former manager at United. The 20-time English champions were keen on the Blues midfielder last summer, but the deal did not take shape.
Matic has featured in 35 league games for Chelsea – which includes 30 league starts - alongside N'Golo Kante. The duo were the two key players in the centre of the pitch that saw Antonio Conte help the Blues win the league in his debut season in England.
The Serbian international's contract with his current employers will run down in 2019. It was believed that Chelsea will hand their star midfielder a new deal after his impressive display. However, Matic is yet to hear from the Premier League winners as Conte is targeting to strengthen his midfield for the next season.
Matic is likely to be dropped down the pecking order if Chelsea bring in new midfielders in the summer. Thus, he has decided to snub Conte and in order to offer himself to United. It is now between the Red Devils and Chelsea to agree a transfer fee. The same report claims that if the two clubs agree a deal, Matic is expected to be Mourinho's first signing of the summer transfer window.
Mourinho has the services of Paul Pogba, Ander Herrera, Marouane Fellaini and Michael Carrick as the first choice midfielders in the squad. Carrick, 35, signed a new one-year deal and he is unlikely to feature regularly next season.
In addition to this, the former Inter Milan and Real Madrid manager sanctioned the sale of Morgan Schneiderlin and Bastian Schweinsteiger earlier in the year. This will force him to bring in a player in that position as he looks to strengthen the squad. Should United sign Matic, he will play the holding midfielder role that will allow Pogba to play a free role next season.