Thomas Tuchel has never met Frank Lampard. They never faced each other as players, either; the latter had a stellar career, the former not at all. They never faced each other as managers, either. The only contact they've had is when Tuchel received a text message from his predecessor the day after he was announced as the new Chelsea boss. Lampard was wishing Tuchel good luck, which surprised and touched the former PSG and Borussia Dortmund manager a lot.

Nevertheless, it would be easy for the German coach who is having a very positive start in England -- Chelsea are unbeaten in his first 12 games, all competitions, since Tuchel took over on Jan. 26 -- to put himself forward by criticizing what came before him. But that's not his style. In private, like in public, he's been asked a lot about what has changed at the club: he keeps telling people that he doesn't know.

"I was not there before. I don't know what Frank was doing, how he was training, so I can't compare. I can't tell you what is different now."

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Of course, this is not completely true. He spoke at length with some Chelsea players before taking the job, like defenders Antonio Rudiger and Thiago Silva, two men he was close to before arriving in London. (Tuchel also coached Silva at PSG.) He exchanged more ideas with other people after arriving at the club as well, and let's be honest: pretty much everything has been different from the Lampard era to the Tuchel era. Said one player: "it's almost like night and day."

The changes aren't just about results. Chelsea were in ninth when he took over. They're now fourth and in charge of the race to finish in the Champions League spots, having beaten Liverpool 1-0 at Anfield on March 4. With a round of 16 second-leg tie with Atletico Madrid (Chelsea lead 1-0 on aggregate) and an FA Cup quarterfinal with Sheffield United (watch LIVE, Sunday 3/21, 9.30 a.m. ET, on ESPN+ in the U.S. only) up next before the international break, here's how Tuchel turned the Blues' season around.

Communication is everything

The biggest thing to change under Tuchel has been the level and quality of communication. There are no more fractures between the manager and some of the members of the dressing room. Everybody is in the same boat. Every player can play, and Tuchel has used pretty much all the players available since his arrival at least once. If a player is selected in his starting XI, he's been transparent with exactly what he wants and what he expects. If someone does not play, he's swift to explain why, either individually or in front of the rest of the group. Under Tuchel, every member of the Chelsea squad and training staff knows exactly where they stand.

He's also done a lot to motivate and re-engage those players who were on the fringes under Lampard. The Chelsea squad is, to a man, more committed, more involved and no longer feeling outcasts if they have a bad game or poor performance.

Not long after he arrived, the 47-year-old coach took Jorginho, N'Golo Kante and Mateo Kovacic aside for a chat. He told them that he would be relying on them to lead by example at the base of Chelsea's midfield, but that he would rotate them depending on the game plan, their fitness and the opposition. In his mind, though, they were all starters. It's worked, too; the trio all bring something different, but they've all performed well throughout Tuchel's tenure.

Tuchel's communication is also visible during matches. He's a vocal coach on the touchline, shouting instructions, offering encouragement or getting frustrated at mistakes. In the 1-0 win at Liverpool -- arguably the Blues' best performance to date under Tuchel -- he notably scolded full-back Ben Chilwell twice in the first half, first for not crossing the ball quickly enough during one attack, and then for picking the wrong target with another cross. In the 2-0 win at Everton a few days later, Tuchel had a go at forward Timo Werner: "Timo, Timo, for how long are you still going to play on the left? You must play on the right! You have been playing on the left for a quarter of an hour. Don't you understand?"

The comments aren't about being mean, but about being perfect. Tuchel is driven by that sense of perfectionism, striving for it with every game. When he substituted Callum Hudson-Odoi off during the 1-1 draw against Southampton on Feb. 20, just 30 minutes after having brought him on, it was not to shame him, but rather to show him that he was not happy with his performance and that he wanted him to learn from it. They had a long discussion the following day in which Tuchel explained to him why he was disappointed, but also reassured him of future opportunities. The young English winger started the next game against Atletico Madrid in the Champions League last-16 first leg. Chelsea won 1-0.

Intensity, intensity, intensity

There is joy again within the squad during training, too. Lampard tried to be a disciplinarian, punishing players in private for issues or mistakes, but that's not Tuchel's style. Last week he admitted he didn't even know what the fine system at the club was -- used when players were breaking club rules or showing up late for training or team meetings -- and has left the dressing room to get on with it.

Privately, he's intimated how much he knows about the history around the club -- that players have gone above the manager to speak to more senior figures during difficult spells -- and has shown little interest in trying to break that up. Instead, his approach has been more holistic, with Tuchel treating his players like adults in the hope he'll get respect that way. He's hinted in media appearances that he's not going to be at Chelsea for years and years, so why not try to make the most of the 18-month or two-year cycle he'll have, rather than fighting against the club culture?

Tuchel has also made sure that his sessions are innovative and entertaining. The players play with small footballs to improve close control; they play basketball, they have fun. They also work extremely hard when asked. The intensity of some drills has risen, more physical and more tactical than before. Tuchel insists on patterns of play, repetition, ball movement and dependable structure from his teams. For example, each player has a "zone" to respect in possession so they can beat an opponent's high press.

Intensity is the key word for Tuchel: he is intense in the job, and everything under his remit has to be intense as well. Everything they work on at training is founded on intensity, whether the aggressive pressing moves Chelsea employ to get the ball back, or their runs with and without the ball.

Training overall is also far more detailed. After the fun and games, there is a plan. They work on the team's shape a lot, they do tactical work on how to beat the press, refine attacking drills and map out defensive transitions, things they never did before. Everything is more technical as well. Tuchel wants control of games and for that, ball retention is essential.

Yet it's not all about rigidity -- Tuchel has also worked with the group to be more flexible when it comes to tactics. The biggest change from Lampard is the formation: Tuchel's Chelsea now play in a 3-4-2-1 formation -- three "central" defenders with support from wide players, and two "playmakers" behind a central striker -- which evolves at times, like in the 1-0 win against Tottenham on Feb. 4, which saw Chelsea in a 3-4-3 with Mount as a "false 9" up front with split strikers in support.

Unlike in Paris, the manager has found a very receptive squad at Chelsea, with no divas or big egos. Said a club source, "[The squad is] all on board. They all work hard. All the players listen to him and do what he says." Tuchel reportedly appreciates having players who listen and a club where he feels he can do what he wants. Before he signed, Tuchel told Marina Granovskaia, Chelsea's executive director, that he wanted to be free to make the choices he felt were appropriate. Put Kai Havertz or Timo Werner on the bench? Drop Tammy Abraham from the squad? Bring back Rudiger or Marcos Alonso back into the team after being frozen out by Lampard? He wanted free rein, and he's since got it.

The players have responded

Since day one under Tuchel, Mason Mount has been the one who made the biggest impression. Tuchel knew of him, but that was it. Upon arrival, he discovered a special player with a huge hunger and desire to learn and improve. What Tuchel loves the most about the young England international is his intensity.

Mount is such a perfect Tuchel player. He has a high football IQ, he is young, learns quickly, can run forever. The manager is always on his players' backs, even Mount. At the start of the second half against Liverpool, Tuchel was visibly unhappy with the 22-year-old's effort despite his superb goal in the first 45 minutes. "Maaason, wake up! Wake up!" he shouted at him.

Tuchel's focus from the start has been to sort out the defence. Chelsea were conceding too many goals and too many chances -- his first task was to stop allowing opponents to move easily into the Blues' penalty area, either by recovering the ball really high or by breaking down the other team's attacks. They have improved massively at the back: much as Tuchel did with his central midfielders, the club's centre-backs have been steadily rotated and partnerships mixed and matched depending on the opponent. While the personnel have changed throughout his tenure -- 23 players have started under Tuchel in 12 games, including all six of the squad's central defenders -- the results have been the same, with just two goals conceded. (He's also been very supportive of Emerson Palmieri, who played in the FA Cup against Barnsley, by talking to him a lot and encouraging him despite an uncertain future at Stamford Bridge.)

The next step is to be better going forward, to score more goals: Chelsea are sixth best in the league this season, with 44 in 29 games. Again, he knows where he is going and how. He has so many options available (Olivier Giroud, Werner, Tammy Abraham, Hakim Ziyech, Christian Pulisic, Mount, Havertz and Hudson-Odoi, to name a few) and will continue to be pragmatic about which player he uses depending on the game plan and the opposition. He is not worried about the finishing because they work on it at training but he wants more chances for his players. In his mind, the goals will come.

Overall, Tuchel is also far more relaxed and happier than he was in Paris towards the end. His objective was to finish the season in the top four, and he's on course to deliver that, making the rest is a bonus. There is the Champions League up next, with a huge Round of 16 second leg on Wednesday against Atletico Madrid. Then comes the FA Cup quarterfinal this weekend against Sheffield United.

Tuchel and Chelsea look ready for a very exciting end to the season. Not only does he look rejuvenated, but a team that was adrift look rejuvenated too.

With additional reporting by James Olley and Gab Marcotti