Fred, who arrived this summer for £52.7m, went to the quarter-finals with Brazil at the World Cup but didn’t play a single minute.
De Gea, on the other hand, has had a decent break after crashing out of the finals at the last 16 stage for Spain to cap off a torrid couple of weeks between the sticks for his country.
Speaking ahead of Man United’s 0-0 draw with San Jose Earthquakes, Mourinho confirmed the pair would join up with the club’s pre-season tour in time for Wednesday’s meeting with AC Milan.
“Step by step we are making the squad ready for the opening day of the Premier League season.”
Nemanja Matic and Alexis Sanchez joined the tour over the weekend, with the latter performing impressively in the stalemate with San Jose.
Piece by piece, United will start to look like more of a recognisable team over the next week. A midfield of Fred, Matic and Ander Herrera offers promise, while the front three of Alexis, Juan Mata and Anthony Martial – all of which will start against Leicester City, according to Mourinho – have a chance to improve as an attacking trifecta.