Ole Gunnar Solskjaer, who was sacked as United manager on Sunday after a 4-1 defeat at Watford, was given the permanent job at Old Trafford only four months after succeeding Jose Mourinho as interim in December 2018.
Questions will inevitability be asked about whether Rangnick could also net the job on a permanent basis if he succeeds over the coming months but United are still focused on hiring an external candidate for that role as things stand. Mauricio Pochettino, the Paris Saint-Germain head coach, remains very interested but is expected to be one of a number of candidates under consideration.
Rangnick enjoyed great success as a sporting director at Leipzig, a club he also coached, and it is not unfeasible a consultancy position with United could become a more formalised role. It also remains to be seen if Rangnick will be given the funds to strengthen an already bloated squad in January.
Having embarked on a serious project with Lokomotiv in which all parties have invested a lot of time and resources, Rangnick is determined to leave on good terms.
Nevertheless, he believes the chance to coach United is a unique opportunity and not one that he wishes to pass up and there was quiet optimism at Old Trafford on Friday of a deal being concluded. The wait for a work permit is expected to preclude him from being in charge for Monday's game at Premier League leaders Chelsea but could be in the dug-out for United's match against Arsenal at Old Trafford four days later.
The Watford defeat was United's seventh in 13 matches in all competitions and left the club in eighth position, six points adrift of fourth place. Rangnick is understood to be in line for lucrative bonus payments if he delivers Champions League qualification via the Premier League or through European success this season.
Michael Carrick, who oversaw Wednesday's 2-0 win over Villarreal that secured United's progress to the Champions League knockout stages as group winners with a game to spare, is due to take charge again against Chelsea.
Carrick, along with fellow coaches Mike Phelan, Kieran McKenna and Richard Hartis, all signed new contracts last month, just weeks before Solskjaer's dismissal, and they are expected to be kept on to work under Rangnick.
United began the process of formally contacting their interim candidates on Monday and Rangnick is understood to have been interviewed by the club's football director John Murtough and technical director Darren Fletcher the next day.
It gave Rangnick less than 24 hours to prepare but he made a big impression during the interview and was the club's unanimous choice to succeed Solskjaer on an interim basis.
"It was very clear he put what little time he had to prepare to excellent use," one source said. "It was abundantly clear he wanted the job and he made damn sure he was going to get it."
Murtough has invested considerable time in recent years travelling around Europe establishing relationships with influential figures on the continent and met with Rangkick in Germany in the autumn of 2019 to take a first hand look at the work he had done at Leipzig in terms of their coaching, academy and overall structural set-up. The pair, therefore, were well-acquainted by the time they sat down for the interview this week.
United believe Rangnick has the experience, expertise, authority and tactical acumen to tackle a difficult job head on and hope he can galvanise a squad low on confidence and in need of direction.
United also interviewed the former Lyon, Lille, Roma and Marseille coach, Rudi Garcia, plus Lucien Favre, the former Borussia Dortmund coach, and Ernesto Valverde, who left Barcelona at the start of last year. Contrary to reports, Valverde was never offered the job and the Spaniard was understood to be the first candidate who was discounted and then Favre.
Garcia spoke to United via Zoom on Tuesday night and then flew to Manchester to cover Manchester City's Champions League clash against Paris Saint-Germain for television before meeting in person with the club on Wednesday. He impressed during the conversations but United's decision-makers ultimately settled unanimously on Rangnick.
Rangnick was at the vanguard of the so-called "gegenpressing" revolution, the Germanic phrase for counter pressing that was adopted by so many of the country's most famous coaches. Jurgen Klopp, the Liverpool manager, and Tuchel are among his many disciples. Klopp has previously described him as the "best German coach" still within the game.