December threatens to sweep away two key pillars of Man Utd.

The 5 vs. 15 figures expose the level of dependence: when Casemiro is present, Manchester United only concede 5 goals; when he is absent, the number jumps to 15. And December, with 6 Premier League matches, plus Bryan Mbeumo and Amad Diallo leaving the club for AFCON, is approaching like a storm that could sweep away the stable foundation that manager Ruben Amorim has painstakingly built.

The December storm and the test of depth

The rocky start to the season has faded into the background, giving way to a five-match unbeaten run in the Premier League. Manchester United benefited from not participating in European competitions and an early exit from the Carabao Cup, thus maintaining a pace of one game per week. This rhythm created an ideal recovery period and allowed Amorim to establish his team's core. But the traditional December – a grueling six-match fixture schedule – will be completely reversed: this is the period that could determine the momentum of the entire season.

The core of Amorim and the irreplaceable cards.

In the current positive picture, four players who start every domestic league game are Luke Shaw, Bruno Fernandes, Matthijs de Ligt, and Bryan Mbeumo. Alongside them, Casemiro, Amad Diallo, and Matheus Cunha are among the players with the most minutes played. This stability stems from habit: the lineup remains largely unchanged, roles are clearly defined, and the tempo of play is well-balanced.

AFCON is recruiting players, so the attacking structure will have to change.

Two absences were anticipated: Bryan Mbeumo and Amad Diallo will return to their national teams for the Africa Cup of Nations at the end of December. This is a major blow to the attack, although Man United had a plan to cope. The problem is that with the attacking threats gone, the remaining key players will have to shoulder a greater burden amidst a packed schedule.

Luke Shaw: Fragile consistency ahead of a two-match-a-week schedule.

At 30, Luke Shaw is playing exceptionally well on the left flank in a three-man defense. Playing only one game a week helps him maintain optimal fitness and avoid muscle injuries – a problem that has plagued him in the past. His injury history shows that Shaw is sensitive to playing two games a week; therefore, the risk of being sidelined in the winter is real. Without Shaw, it's not just a loss of a left-back, but also a broken link in the defensive system.

Casemiro: peak form and questions about tempo.

Casemiro, at 33, remains resilient, and this season has seen a clear resurgence. The numbers speak for themselves: Man United have conceded only 5 goals when he's on, and 15 when he's absent. However, last season's resurgence largely occurred at the slower pace of the Europa League, while the domestic league is much more demanding. December, with its two games a week schedule, raises the question: can Casemiro maintain the intensity and quality of his pressing, interceptions, and ball distribution at the current level?

Amorim's rotation problem

Amorim benefited from team consistency during the game-per-week period. But December doesn't allow for that repetition. Rotation is mandatory, and any cracks – Shaw's injury or Casemiro's dip in form – can quickly spread throughout the team structure. Yesterday's "invincibility" may have to give way, simply because the body and rhythm of play don't lie.

Selective statistics

• A run of five unbeaten matches in the Premier League has given Man United a boost of confidence.
• Four key players who start every domestic match: Luke Shaw, Bruno Fernandes, Matthijs de Ligt, Bryan Mbeumo.
• Casemiro's appearances: conceded 5 goals; his absences: scored 15 goals.
• December: 6 Premier League matches, at a rate of 2 matches per week.
• Mbeumo and Amad Diallo will participate in AFCON at the end of December.

Man United have been on the right track thanks to a stable system and a sensible rhythm of play. The upcoming festive season will determine whether that foundation is strong enough to withstand the storm. If Shaw maintains his fitness and Casemiro sustains his form, the road ahead will be wide open; otherwise, December will be the most challenging turning point that will halt their progress.