The German will take charge until the end of the season – but the offer of a two-year consultancy role is what convinced him to answer the call from Old Trafford after rejecting a similar approach from Chelsea in January.
United still plan to press ahead with the search for a permanent successor to Ole Gunnar Solskjaer at the end of the season, with Mauricio Pochettino a leading target. But by ensuring Rangnick is linked with the club beyond his six-month interim contract, they have given themselves the opportunity to include him in that process.
The 63-year-old was already considered a candidate as a permanent appointment, alongside Pochettino, Erik Ten Hag, Brendan Rodgers and Zinedine Zidane.
Although United have been able to bring him in now, they are intent on sticking with their original plan of waiting until the summer to make a final decision.
But if Rangnick has a transformative effect on their campaign, it would place serious doubts over Pochettino’s hopes of securing the job he has long-craved.
Solskjaer was appointed ahead of the former Tottenham manager in 2019 after making a spectacular start as interim.
United already believe they have landed one of the greatest thinkers in modern management – and it could become impossible to let him go if he impresses.
But, as it stands, the club insist they are not looking beyond the end of the season and will continue their recruitment process over the next six months.
United are hoping to tap into that expertise on the pitch, but also want him to help shape the future direction of the club after Solskjaer became the fourth manager to be sacked since Sir Alex Ferguson’s retirement in 2013.
He is not expected to be in position for Sunday’s clash with Chelsea as he awaits a work permit, but could be in charge for Thursday’s game against Arsenal.
Pochettino, meanwhile, will hope to strengthen his case by leading Paris St-Germain to the French title and perhaps the Champions League.
The Argentine wants the United job and was believed to be prepared leave the French giants immediately if granted permission.
United were also keen on him, with Sir Alex Ferguson a leading supporter, but the club feared protracted negotiations with PSG would further derail their season.
They were conscious of the Qatar-backed club’s response to Kylian Mbappe’s attempts to force a move to Real Madrid in the summer – and did not want a repeat with Pochettino at a time when their campaign has gone into free fall.
The immediate priority was to stabilise the season, with Rangnick considered the overwhelming candidate to do that.