I'd say if Bellingham, Mbappe, Vini and Rodrygo don't suffer injuries, Madrid's performance will be stable. These 4 are the most important players in Madrid's squad at the moment. If the bonding between these four players is strong, Madrid's overall performance will be even stronger.
These 4 players are very important to Real Madrid but I don't think they're the only ones you should b praying to avoid an injury. The midfield and defence don't have enough depth too. An injury to Valverde or Camavinga can be a problem. In defence, Madrid have only Militao and Rudiger currently fit for centre-back positions, if an injury is to happen to any of them then there will be trouble.
So even if Bellingham, Mbappe, Vinicius and Rodrygo don't get injured, the team might be in serious trouble if more midfielders and defenders get injured.
The success of Madrid this season might rely solely on the chemistry between their front line. The wings need to be in sync because Madrid will rely on them to create chances and score goals since the midfield can't create chances.
Real Madrid had formed a strong team but injuries messed up all their plans. They bought Mbappe and released Toni Kroos from their club last season to play Jude Bellingham in midfield. Valverde has problems, so Real Madrid's plan may be different in the upcoming matches.
Real Madrid have plenty of support players but without players on their bench who are at least as skilled as those who have performed in the starting XI in important matches, it will be challenging for them to win against any team. But the defense is still strong, so this defense is now the hope of Real Madrid.