Former Manchester United midfielder Phelan worked as assistant to Ole Gunnar Solskjaer, but Ralf Rangnick’s arrival as interim boss saw his influence reduced as he became a first team coach.
Phelan was not involved in first team training sessions, but he is set to see his fortunes change under Ten Hag.
The 59-year-old is set to have a bigger role as part of Ten Hag’s backroom staff and the Dutchman will be looking to utilise his knowledge of the English game to the full.
Ten Hag’s new-look Manchester United will kick off their pre-season preparations by taking on Liverpool in a friendly clash in Thailand.
They then lock horns with Melbourne Victory, Crystal Palace, Aston Villa, Atletico Madrid and Rayo Vallecano.
Manchester United’s Premier League campaign gets under way with a visit from Brighton on 7th August.
Ten Hag’s men have so far been quiet in the summer transfer window, but they are working on deals for several players.