The Morocco international spent the second-half of last season on-loan at United, helping them win the FA Cup.
His deal included a permanent option, but United wish to talk down that original price.
Agent Giulio Tedeschi told FirenzeViola: "Right now, in my opinion there is a concrete possibility of bringing Amrabat back to Manchester United. In my opinion there was some doubt also because it was not known whether Ten Hag would stay.
"Now that it’s certain that he will stay, there are grounds to think about bringing Amrabat back even on loan with obligation, or at a lower figure. The United solution is the easiest. I believe Amrabat’s renewal with Fiorentina until 2026 was done deliberately to help La Viola gain strength. It’s a tactic that clubs do to gain bargaining power.
"If it’s not €20m (£16.8m), it won’t even be €10m (£8.4m). It will be a mid-range figure, trying to maximise his sale."