The Uruguay striker has impressed at the World Cup finals in South Africa, netting three goals to help his country to a place in the semi-finals.
Forlan now plies his trade with Spanish side Atletico Madrid after two unsuccessful years at United saw him move on from the Premier League club.
The 31-year-old managed just 10 league goals during his time at Old Trafford, but the frontman has since transformed his career in La Liga.
And one of United's backroom staff - Rene Meulensteen - revealed he would happily see the former Independiente man back in a Red Devils jersey on his current form.
"I told him, 'what you learn here, you will take with you'. You are a player who adds something to every squad.
"He has developed fantastically, so complete - a top athlete. I really would welcome him back to Manchester United."
Meulensteen said he sent Forlan a text message after he netted both goals in the victory over Fulham, reading: "Top class, if it's up to me you will return to us."
The striker reportedly replied: "I am ready for it."