The England midfielder had a transfer request rejected by United last month, though appeared still determined to leave during the January transfer window.
However, with former manager Amorim now gone, Mainoo is rethinking his future at Old Trafford.
A United source told The Sun: “Kobbie was frustrated under Amorim because he felt like he broke into the first team and gained a lot of success playing one way.
“Then suddenly Amorim started telling him he needed to play in a completely different way, which wasn’t to his strengths.”
Talks over a new contract have stalled this season, though the situation could now change with Mainoo feeling better about his status at United.
The source added, “Amorim leaving definitely increases the chances of Kobbie staying at United. But it’s not a given.
“He wants assurances from officials about how they see him fitting into the squad and the first team.”