The American was a likely candidate to succeed Marcelo Bielsa at the close of the 2021/2022 season, but the sacking of the former United manager forced the move to progress quickly.
In February, Marsch was offered the chance to take charge of a team in crisis with the huge mandate of steering them clear of relegation - and he wasn’t completely sure whether or not to accept.
“I knew there was an opportunity when Victor [Orta, director of football] asked me to come at a time that I, frankly, didn’t want to come,” Marsch said.
“From the beginning, when Victor asked me to come - at first I was like ‘no’. Then I thought about it for 24 hours and it was an opportunity.”
The Whites wrapped up their first signing of the summer transfer window on Thursday, with USA international Brenden Aaronson joining the club on a permanent basis from RB Salzburg.
Check out the latest Premier League transfer speculation below...
1. Ebiowei in demand
Derby County youngster Malcolm Ebiowei is at the centre of a four-way battle this summer, with Manchester United and Newcastle United joining Tottenham and Crystal Palace in showing interest in the 18 year-old attacker. (Daily Mail)
2. Hammers willing to sell Soucek
West Ham will listen to offers for Tomas Soucek this summer following a row with David Moyes. (Football Insider)
3. LONDON, ENGLAND - MAY 22: Demarai Gray of Everton in action during the Premier League match between Arsenal and Everton at Emirates Stadium on May 22, 2022 in London, England. (Photo by Mike Hewitt/Getty Images)
Newcastle United have mentioned Everton winger Demarai Gray as a potential summer transfer target. (Daily Mail)
4. Leeds rekindle Ivanusec interest
Leeds United have reignited their bid to sign Dinamo Zagreb attacker Luka Ivanusec. Marcelo Bielsa was said to be a ‘big fan’ of the player, and the Whites were previously linked with a £12.7m swoop for the Croatian international. (Germanijak)
5. Villa lead McNeil race
Aston Villa are leading Everton and Wolves in the race to sign Burnley winger Dwight McNeil. (SkyBet)
6. Leeds could face ‘impossible’ Phillips call
Leeds United could find it “impossible” to turn down Manchester City in Kalvin Phillips if they follow up their interest in the midfielder with a substantial offer. (Mirror)