Sometimes Thomas Tuchel concentrates so hard that he can't see a person standing a yard beside him. He must feel like that this week.

On Tuesday, the giant, obsessive manager sends his weakened, Neymar-less Paris Saint-Germain side out against a resurgent Manchester United. If PSG wins, the club remains on track for its last remaining obsession and, frankly, almost the sole point of its existence these days: its first-ever Champions League trophy. (So dominant is Paris at home that nobody is excited about its impending sixth French league title in seven seasons.)

Off the field, Tuchel has another objective: getting his nemesis, Antero Henrique, replaced as PSG's sporting director by his soulmate, Arsene Wenger. This is the German's chance to establish himself as the long-term guide of a giant club rather than just the latest of PSG's seemingly temporary coaches.

Like Wenger, Tuchel reached the top solely on drive and brainpower. He, too, was a modestly talented defender whose true passion was coaching. After injury ended his playing career at third-division Ulm, aged just 24, he coached youth teams at Stuttgart, Augsburg and Mainz, graduating from a coaching course with sky-high grades. After Mainz suddenly offered him a job coaching the first team -- the first time he had ever coached adults at any level -- he went on to win more points than all but four other Bundesliga teams in five seasons. He then quit, saying he couldn't take the club any further. In his next job, at Dortmund, he had the unenviable responsibility of replacing Jurgen Klopp but arguably went on to be better; his points-per-game average (2.09) was the best of any coach in the club's history. Yet Tuchel quit in 2017 after clashing with team executives and, after a sabbatical, he joined Paris.

And so, an awkward character had taken on an awkward club. If PSG's stars had been the kind of people who wanted to push themselves to the maximum every week, they wouldn't be playing in the tinpot French league. And nobody can tell Neymar, Dani Alves or Kylian Mbappe what to do. Tuchel understands that the coach isn't the most important man in any club; he describes soccer as a "players' game." But how does one manage this squad?

Thomas Tuchel is an obsessive manager who tries to leave nothing to chance. PSG will need every bit of his focus in the weeks ahead. Jan Kruger/Getty Images

Tuchel arrived having taught himself very decent French (better than some players who have been at PSG for years). That helped him woo PSG fans: "Too-shell," as the French mangle his name, is more popular than his predecessors. However, language is also essential to his work. Tuchel believes in deep communication that's different for every player. He obsesses about what makes each man tick.

At Mainz, writes German author Christoph Biermann in his book "Matchplan," Tuchel discovered that one of his players was motivated by money: namely win bonuses and the dream of a lucrative transfer. That was fine by Tuchel; understanding this made the art of man-management easier. At PSG, he decided that what the squad's many Brazilians most wanted from a coach was love. Tuchel says he hugs Neymar and that when the player isn't around, "I write him texts to tell him I still believe in him and that I'm sad he isn't here." This was not the approach taken by his predecessor, Unai Emery.

Yet Tuchel also subjects PSG's players to his fanaticism. Rail-thin at 45 years old, he boasts of having once spent four weeks in Italy without touching either pasta or pizza. The first time his PSG side took the bus to an away game, the playmaker Marco Verratti requested a Coca-Cola. Horror of horrors, he discovered that Tuchel had banned all soft drinks and sandwiches. Verratti quickly got the message.

Discipline has long been an issue at PSG. Players kept forgetting bits of kit in the changing rooms during training and going back to fetch them. Showing up late for meetings was epidemic. Eventually, Tuchel punished Mbappe and Adrien Rabiot by benching them for the grudge game against Marseille last fall (of course, PSG won anyway). He has also reportedly gone around his players' favorite restaurants and nightclubs to have a word with staff.

Tuchel's pushed his team in a tactical sense as well. For years, PSG had only one gear: an attacking, possession-based 4-3-3. But Tuchel is a believer in constantly changing formation and in attacking through the center of the field rather than the flanks. PSG can now play in a 3-4-3 and even run on the counterattack.

Their start to the season was excellent: PSG reeled off 14 straight league wins, a French record, and earned a slightly lucky qualification for the Champions League knockout stages after a crucial 2-1 home win against Liverpool. But things unraveled this winter.

In December, Henrique kicked Rabiot out of the squad because the midfielder refused to sign a new contract. Then, on Jan. 23, Neymar broke his metatarsal bone again. He will miss the United games. So, almost certainly, will Edinson Cavani, after he limped off during Saturday's 1-0 home win against Bordeaux. With Verratti only just back from injury, Tuchel is struggling to field a midfield against Ole Gunnar Solskjaer's suddenly invincible side.

PSG's run of injuries is terrifically unlucky, but it also reveals a flaw in the club's recruitment strategy: After it paid a combined transfer fee of €400 million for Neymar and Mbappe, the two most expensive players in soccer history, there wasn't enough left to build a deep squad.

Cavani's injury over the weekend, which puts him on the sidelines along with Neymar, could be a problem vs. Man United. It's yet another issue for Tuchel to address. Jean Catuffe/Getty Images

Since the New Year, Tuchel's previously unbeatable team has crumbled. It lost at home to village team Guingamp; it lost away to Lyon; and on Feb. 6, PSG needed extra time to beat third-division Villefranche in the French Cup.

Meanwhile, Henrique has been flailing off the field. Last summer, he failed to sign the defensive midfielder, which was Tuchel's priority. Days before the January transfer window closed, with Tuchel asking for two new midfielders, the Portuguese still hadn't even managed to sign one. The young Argentine midfielder Leandro Paredes was expected to join from Zenit St. Petersburg, but in late January, Tuchel half-joked, "I've looked for him in the showers, in the changing room, with the janitor, the physios ... but he's not there!" Paredes eventually arrived before the deadline, but he alone may not be enough.

Henrique's longer-term project of signing midfielder Frenkie De Jong from Ajax failed too, despite long hours of negotiations in Amsterdam's Amstel Hotel. Perhaps predictably, the player chose Barcelona.

Tuchel is cautious when responding to questions about Henrique -- "I have my views, he has his" -- but the two plainly aren't best friends. Tuchel's exit from Dortmund after his clashes with directors there suggests one possible ending in Paris, but there's also a more hopeful scenario for him: that Wenger replaces Henrique as sporting director. Nine months after leaving Arsenal, the Alsatian, 69 years old but still looking more like 40, is bored and keen to return to daily soccer.

Wenger has advised the club's Qatari owners from the start. In 2011, he told them it was a "no-brainer" to buy the club. He has long been a well-paid pundit on the Qataris' French TV channel, BeIN Sports. He has received many offers from clubs and federations in recent months, but the job he appears keenest on is Henrique's.

Tuchel is a coach in Wenger's own image: a cerebral, multilingual workaholic obsessed with diet, match stats and beautiful football, and -- so far, anyway -- not a serial winner of trophies. In fact, Tuchel hasn't yet won a single title. But Wenger doesn't want to join PSG only to spend his days fighting: He wants long-term control. That would mean Henrique leaving.

A Tuchel-Wenger duo able to unleash Neymar and Mbappe would be something to behold. But first, an under-strength PSG team must somehow find its way past United.