They were so good that Nagelsmann was poached by Bundesliga champions and European giants Bayern Munich. The manager departed Die Roten Bullen following a 4-1 loss to Borussia Dortmund in the DFB-Pokal final, which was a very disappointing defeat for Leipzig.
Despite finishing in second, they failed to record a victory over league rivals Munich and Dortmund. Die Roten Bullen lost once and drew once versus Bayern, and they lost all three of their matches against BVB.
Now, with a new head coach in at the Red Bull Arena, will Leipzig finally be able to assert their dominance and become the major football powerhouse in Germany?
New head coach
The departure of Julian Nagelsmann left many wondering what the club had in store for the future, and who'd be the one leading them into that future.
In his two years at Salzburg, Marsch was a huge success. He did the double in both of his seasons there, winning the Austrian Bundesliga as well as the Austrian Cup twice.
He also gave league debuts to the likes of Erling Haaland and Dominik Szoboszlai, who have both since moved on to the German Bundesliga. Haaland is with rivals Borussia Dortmund, whereas Marsch will get another chance to work with Szoboszlai as the midfielder is currently contracted to Leipzig.
Die Roten Bullen have played three pre-season matches thus far, winning one, drawing one, and losing one. However, the results are not what's key here.
These games have given the players an opportunity to understand the style of play Jesse Marsch is trying to implement in the side, as well as building the chemistry between the players new and old.
Leipzig defeated Dutch outfit AZ Alkmaar 1-0 in their opening pre-season contest, with youngster Lazar Samardžić grabbing the only goal.
They then went on to lose 2-1 to Montpellier, with Alexander Sørloth getting onto the scoresheet for Die Roten Bullen.
Leipzig have been very busy this summer, with some new key players coming into the club, as well as a number of key outgoings.
The two biggest departures have to be Dayot Upamecano and Ibrahima Konaté. Both players left the club with big transfer fees, which sees Die Roten Bullen make a huge profit margin on the youngsters. Upamecano sealed his move to Bundesliga giants Bayern Munich, and Konaté signed with English powerhouse Liverpool.
Defensive acquisitions have come in Josko Gvardiol, a 19-year-old centre-back from Croatian champions Dinamo Zagreb, as well as another Frenchman in the form of Mohamed Simakan, a centre-back signed from Strasbourg. Both signings are seen as replacements for the aforementioned Upamecano and Konaté, and they are likely to battle amongst each other for a starting spot next to Willi Orban.
Leipzig's marquee signing of the summer has to be André Silva, as the forward joins from Eintracht Frankfurt following a successful 2020-21 season. Silva finished second in the Bundesliga scoring charts with 28 goals, ahead of Erling Haaland, and he also had eight assists.
Talented winger Justin Kluivert hasn't signed a permanent deal with Die Roten Bullen, so he will not be returning for this season. Hannes Wolf has also left the club, signing permanently for Borussia Mönchengladbach.
Leipzig have confirmed the permanent transfers of former loanees Angeliño and Benjamin Henrichs, who are two signings that give them extra strength in the full-back positions.
Another astute acquisition is that of Brian Brobbey on a free transfer from Ajax. The 19-year-old impressed at the academy level before getting promoted to the senior side last season, making almost 20 appearances in all competitions, scoring six goals and providing two assists.
Leipzig's key player for the 2021-22 season has to be summer signing André Silva. A number of players will play a large part in any success the club has this season, as they have a strong core to the side, but the striker's attacking returns could make all the difference at the end of the day.
Already a proven goalscorer in the league, Silva will now have the tools to score more and create more as well thanks to the strength of the squad at Die Roten Bullen.
The likes of Christopher Nkunku, Emil Forsberg, and Marcel Sabitzer will be able to provide the Portuguese forward with almost endless opportunities throughout the season, which could see him have even more goals than he had at Frankfurt last season.
If Leipzig are to push Bayern all the way until the end of the campaign, Silva will have to deliver on a consistent basis. Luckily for them, he seems up for the challenge.
A breakthrough talent at Ajax last season, Brian Brobbey could be the next big thing at the Red Bull Arena.
His opportunities in the league might be limited due to Leipzig's firepower up top in the form of Silva, Sørloth, and Yussuf Poulsen, but Brobbey's rise could come in cup competitions.
Brobbey has been nothing short of prolific in front of goal for the Netherlands' youth sides, scoring 25 times in only 35 appearances from the U15's up to the U17's.
His transition into senior football has been impressive too, as he's already featured in the Eredivisie, Champions League, and Europa League. The Dutchman scored three times in the Europa League, bagging against LOSC Lille, BSC Young Boys, and AS Roma before Ajax ultimately departed the competition in the quarter-finals.
There is no doubt that Brobbey is talented, but he'll have to give it his all in order to showcase his ability at this sort of level.
Leipzig's season gets underway this Saturday, as they visit SV Sandhausen in the first round of the DFB-Pokal. Their Bundesliga campaign gets underway the following weekend with an away trip to Mainz.
Die Roten Bullen will certainly see their matches against Bayern Munich as key fixtures, as they are must wins if they are to challenge for the league title. Leipzig hosts Bayern on matchday four on September 11th, and they will travel to Munich for the return fixture on matchday 21 on February 5th.
Other key fixtures are those against Borussia Dortmund. Leipzig hosts Dortmund on matchday 11 on November 6th, and they travel to the Signal Iduna Park on April 2nd for matchday 28.
Die Roten Bullen fans will hope that Jesse Marsch is the one who will finally pip Bayern to the Bundesliga title, but for me, Leipzig will have similar fortunes to last season.
They certainly have enough talent to push Bayern and cause problems towards the top of the table, their frontline has obviously improved since last season, and they are likely to create more in front of goal. However, Marsch will need time to implement his ideas and for the players to gain an understanding of what he wants.
Losing the centre-back pairing of Dayot Upamecano and Ibrahima Konaté could also play a huge factor. Their new young defenders have a huge job on their hands, as replacing the French duo won't be easy.
Julian Nagelsmann signing with Bayern could have a huge impact on the title race too. He obviously knows the ins-and-outs of Leipzig, which could make it very difficult for Die Roten Bullen to get a result against the Bavarians.
Another top three finish for Leipzig looks very likely, but a battle between Leipzig and Dortmund for second place seems more likely than Die Roten Bullen claiming their first ever Bundesliga title.