The good thing is Xabi Alonso has a system that works, the bad thing is that systems stop working when the things that made the system work are gone. This is what could turn into a problem for Alonso when his players leave for the games with their national teams. There can also be injuries, which if a key player is affected cannot be underestimated as hardly any team has the player resources like Bayern Munich to make up for that without losing quality. The question about the validity of the system has been answered, it works. But whether all parts remain intact is the question now.
Injury is one of the risks that can occur when conditions on the field are not conducive, so that playing on the field becomes unhealthy and unpleasant. However, Xabi Alonso must still have a backup strategy to still win the upcoming match in January next year. At least there is still sufficient time to recover the condition of the injured players, and there is sufficient time for Xabi Alonso to find a solution to the problem that is currently affecting him.
It's true that Bayer Leverkusen doesn't have quality players like Munich, but Xabi Alonso's strategy cannot be underestimated, even though Bayer Leverkusen doesn't have a striker as sharps as Munich, in fact Bayer Leverkusen can still appear impressive and undefeated to date, so I think even though at this time Bayer Leverkusen Xabi Alonso is experiencing injury problems, he must have thought of other options to replace the position of the injury player, or at least Xabi Alonso is recruiting new player in January to further strengthen the depth of their squad.
Bayer Leverkusen was built with strong chemistry and Xabi Alonso's tactics are very suitable to be applied with the existing player material.
To build a strong squad you don't always need star players, but the players currently at Bayer Leverkusen have fairly even quality in each line so they can produce quite good performances from the start of the season.