The Portuguese coach is believed to be keen on making sure that the players are solely focused on what they need to do on the field rather than be distracted by their contract situations.
According to The Independent, the futures of Fellaini and Rashford are priorities, while there is also growing confidence that Ander Herrera will pen fresh terms.
Fellaini has had many critics during his four years at Old Trafford, the majority of which came from the club's own fans, but the midfielder is well liked by Mourinho due to his ability to carry out key plans.
Rashford has become a regular inclusion in the first-team squad since breaking through in 2015, making 49 top-flight appearances so far, scoring 12 goals and creating four assists.
New deals are expected to be offered to both Fellaini and Rashford, whose current contracts expire in 2018 and 2020 respectively.