Was it for the cameras or was it genuine?

On Tuesday night, just after half-time as the Paris Saint-Germain players were about to return to the pitch for the second half at Nantes, Thomas Tuchel grabbed Kylian Mbappe by the waist and whispered some tactical instructions in his ear, then patted him on the back in encouragement. The German manager knew very well that the cameras were there, watching. He knew because before, during and after PSG's 2-1 win at Nantes, all eyes were on Tuchel and his superstar No. 7.

Three days after the 5-0 win over Montpellier at the Parc des Princes where, unhappy to be taken off after 69 minutes, Mbappe clashed with his coach, all eyes were on the pair, with fans and pundits looking to glean any little detail in their relationship at the Stade de la Beaujoire.

Tuchel gave his version of events on Saturday when he said: "I am the manager. It is me who decides who comes off and comes on. Kylian is very clever, he knows what he has done. He doesn't like to be subbed off, no player likes it. It doesn't give a good image but we are not the only club where it happens." Later, he added: "We play football, not tennis. We have to respect everyone."

Of course, the tension has eased a bit between them since the weekend, as we saw on Tuesday. Their clear-the-air discussion on Sunday at the training ground, according to sources, probably helped a lot. It's important to note that Mbappe didn't apologise to Tuchel in private or in front of the squad, but did admit that he may have overreacted. Tuchel explained that he took his striker off to give Edinson Cavani some game time and also to give Mbappe a rest, a fair justification. Nevertheless, there's clearly an issue there, and it's not the first time the two have clashed.

Mbappe -- who is ranked No. 3 among the world's top forwards in ESPN's FC 100 -- was dropped from the starting XI last season for Le Classique in Marseille. He wasn't happy to be on the bench for a Champions League group game at Club Brugge earlier this season either, making his frustration clear after he scored a hat trick in just 21 minutes after coming on as a second-half substitute: "I wanted to show that you cannot not play me." The score was 1-0 prior to Mbappe's involvement; of course, PSG ran out 5-0 winners thanks to Mbappe's heroics.

The 2018 World Cup winner was even less content to be subbed off against Nantes on Tuesday, or against Montpellier on Dec. 7. Each time, it seems that the two men, so key to PSG's fortunes this season, are drifting further apart.

Tuchel can't have one of his players, whomever it may be, publicly undermining his authority. He has to be strict as the coach of this high-powered team, and discipline has always been an important element of his management style. There are rules and players, regardless of their standing or status within the squad, have to respect them. Looking at the bigger picture, Mbappe cannot play every minute of every game in Ligue 1, the Coupe de France, the Coupe de la Ligue and the Champions League. He can't go to the Euros and to the Olympic Games, as much as like he would like to. He might be only 21, but it would be irresponsible to put that many minutes into his legs every week.

From Mbappe's perspective, he believes his manager is treating him like a U19 player, not like the superstar he is and certainly not like the club's biggest asset. He reportedly reminds everyone around the club that Neymar never comes off and that even Angel Di Maria is substituted less often. The club tells Mbappe repeatedly that he is valued, is a huge part of the project and is a key player, yet he doesn't sense the same message coming from the manager. The former Monaco prodigy, for example, feels that Didier Deschamps gets him and knows how to handle him. Not so much Tuchel.

At a time when PSG are trying to reinstate the importance of the institution over player power inside the dressing room, this is a watershed moment. Leonardo is back at the club as sporting director to bring the authority back at the highest level. We saw his resolve when he stood firm in the Cavani transfer saga with Atletico Madrid, though the club has to be careful with Mbappe.

PSG have already offered Mbappe a new deal to remain at the club, with his existing contract ending in 2022, and the new one reportedly would make him one of the top earners in world football. His camp will make a decision once the domestic season is over, and the club is quietly optimistic. However, you can't help but think that the feuds between Mbappe and Tuchel could have an impact on the striker's thinking in the coming months.

Some in France think that things could reach a point where the pair can't continue together at the same club and that PSG would have to choose one or the other. In that case, it's pretty easy to think whom they might keep. It's perhaps far-fetched to think this feud gets to that kind of ultimatum, but this tension is certainly not good for the club and it doesn't reflect well on anyone.

At the moment, both Mbappe and Tuchel are focused on making this season a success. They will win the league, and probably the domestic treble too. The Champions League is the biggest challenge, and PSG (who, according to FiveThirtyEight's Soccer Power index, are fourth-favourites to lift the trophy) can only do well if the atmosphere in the dressing room is positive. Tuchel needs to sense that all the players are fully behind him and trusting his decisions. The players need to believe that his decisions are the right ones, too.

They're not there yet, and they will have to get it right -- and quickly.