The American celebrated as if it was the greatest moment of his life and said afterwards that he would remember Joe Gelhardt's injury-time winner on his "deathbed" - it really did feel that important.
Somehow the Whites had managed to find themselves at 1-1 with bottom of the table Norwich City with time running out. They should have been out of sight, but whether through nerves or whatever they had allowed Norwich to creep into the game in the closing stages.
And when the Canaries equalised Rodrigo's early strike for Leeds in the first minute of injury time the knives were being sharpened for Marsch and owner Andrea Radrizzani if it was to be three games without a win for the recently appointed coach on top of the four losses that ended the Bielsa reign.
However, Marsch thought quickly. He had a substitute left and threw on Joe Gelhardt in a last desperate move - and how that paid off.
First, a long ball was flicked on by the teenage forward, then Raphinha came up with a piece of high skill to get away from a defender and round keeper Tim Krull. The angle was tight, but the Brazilian found a perfect pull back to give the supporting Gelhardt the chance to gleefully add to his growing hero status with a simple finish.
The roof almost came off Elland Road and celebrations all round the ground made it feel like Leeds had won the league never mind, just managed to go in front in a game they had totally dominated for 70 minutes.
And still there was more drama as Leeds stood like statues in defence as Norwich mounted one last desperate attack and only a fantastic point blank range save by Illan Meslier denied Teemu Pukki another equaliser in the eighth minute of stoppage time.
To the relief of most of the 36,321 in Elland Road - not least of all Marsch - referee Stuart Attwell blew the final whistle moments after this last attack and three precious points were in the bag.
Marsch was left to explain away an incredible incident-packed game which had seen the back to his best Raphinha hit the woodwork twice, chances galore missed by the home side and Norwich also hit the crossbar as well as having a penalty given by Attwell only to have it taken away by VAR ref Mike Dean.
He said: "I feel like I played 96 minutes.
"There's a lot of emotion in the late stages of the match. I heard a lot about the magic of Elland Road, it was certainly an incredible experience.
"They asked me before will I remember this in two weeks. I said on my deathbed.
"The last moments of the game you really feel the energy. Throughout the game, the difference between Villa and this was we performed with confidence and aggression and quality and it brought the crowd into the game and gave them something to root for and be attached to.
"Jacko (Mark Jackson) said before the game when people come to Elland Road, they know they’ll see a fight, a team that pours their heart and soul into the match. We wanted to make sure after Villa that we did that in a better fashion to represent the club and community. That we showed.
"The three points are incredibly valuable. But regardless of the result, the performance was strong.
"It’s a big step forward - not just points but clarity on the pitch tactically.
"There's still so much work to do. I promise you that there's still so at every moment there's still little tactical positioning and ideas and connections that can be better and need to be better. But that was a step in the right direction. in many ways and we will certainly use it positively to help us move forward."
Marsch was pleased with Patrick Bamford's return to the starting line-up, although it was always planned that he would be restricted to the first 45 minutes, and he explained why Rodrigo was taken off in the second half.
He said: "Very happy with Patrick, impactful 45 minutes,
"I’m satisfied that’s all we needed, from him, 60 was too much. It was clearly enough at half-time.
"Rodrigo and I got to know each other well in the last few days, talked a lot about vision for him, in the team, how to help, how to believe in the transition. He’s a good young man, a quality player - not just the goal but how he played.
"He's an honest man, he's willing to have hard conversations and open conversations. And I know he wants to help and I'm just trying to instil belief and instil an idea of how he fits in and how off the field and on the field he can be a massive presence for the entire team.
"So he, I think he took our conversation really well, as did I. And I think he applied himself really, really well today, really, really well. And then you know, I think on another day if he if he doesn't feel the tightness in the quad, he could probably help us find the second one and continue to push in the match.
"Patrick I would guess is fine. Rodrigo, we’ll have to see. He has tightness in his quad, not an injury, we’ll see how he recovers over the next few days."
Marsch also explained what the dramatic winning goal could do for youngster Gelhardt.
He added: "I don't think Joffy will ever forget that moment, either.
"He's a brave young man. He's got quality. And so I'm going to invest in all these young men and try to help them understand within the framework of the system that we're creating here.
"So yeah, really happy for Joffy and obviously in a tough moment for the club and for the team he comes on and make a big play."
Leeds were given the boost of an early goal as they were ahead in the 14th minute when Rodrigo's strike went in via a deflection.
It could have been ruled out as Bamford had been inches offside in the build-up, but as he did not touch the ball it was deemed he had not interfered with play.
A goal ahead, the Whites settled to look more like the team Bielsa had managed with some swift attacks that cut open the visitors for much of the rest of the opening half.
A great move saw Raphinha combine well with left-back Stuart Dallas only to see the Brazilian miss-hit his shot in the area.
Even better play followed with Raphinha playing a 40-yard crossfield ball to Bamford then getting on the end of Bamford's cross only to see his volley come back off the crossbar with Krul unable to move.
From a corner moments later Pascal Struijk's header was well saved by Krul and the rebound fell nicely for the defender, but he fired over when it looked easier to score.
Another Struijk header from a corner was more comfortably saved by Krul before Milot Rashica sent a 25-yard free-kick over as Norwich briefly got in the game.
United then had a huge penalty shout waved away by referee Attwell after Dan James was barged off the ball in the area.
Bamford hit a shot over from the edge of the box and combined with Raphinha again soon after only to shoot wide with only Krul to beat. Somehow Norwich had made it to half-time only one down.
Leeds continued to do the pressing in the early part of the second half with James putting the ball in the net from a rebound following Raphinha' shot only to be correctly ruled offside.
Mateusz Klich put over a clever pass over the City defence, but Raphinha could not get on the end of it. Dallas's cross hit Ben Gibson on the arm anad again no penalty was forthcoming.
Krul came to Norwich's rescue again with a flying save to keep out James' curling shot while Diego Llorente sent a header wide from a corner.
The second goal would not come and the visitors gradually worked their way into the game with sub Jonathan Rowe forcing a save from Meslier with a deflected shot.
Rowe went even closer soon after with a snap shot in the box that beat Meslier only to hit the crossbar.
A big moment followed when Rashica went down in the box and Attwell pointed to the spot. Replays showed the Norwich player had in fact made contact with Luke Ayling not the other way round and after a VAR intervention the spot kick decision was reversed.
Relieved United got their game going again and could not believe their luck as Raphinha's 25-yard free-kick hit the crossbar.
As the board went up for six minutes of added time Norwich took their chance to equalise as Pukki got round Struijk and saw his cross turned in by Kenny McLean, arriving from midfield.
It seemed like all United's good work from earlier would come to nothing, but Gelhardt's winning contribution changed that along with Meslier's late, late save ensuring the vital three points were in the possession of Leeds.
(Rodrigo 14, Gelhardt 90+4)
Norwich City 1
Sunday, March 12, 2022
Leeds: Meslier; Ayling, Llorente, Struijk, Dallas; Forshaw, Klich (Gelhardt 90+2); James, Raphinha; Rodrigo (Koch 60), Bamford (Harrison 45).
Norwich: Krul; Aarons (Gilmour 88), Gibson, Kabak, Williams; Lees-Melou, McLean, Rupp (Normann 45); Sargent (Rowe 62), Pukki, Rashica.
Referee: Stuart Attwell