My guess would be this is about Zinchenko being unfit, but maybe also a decision to jettison the tactical pattern where Zinchenko's been tucking into midfield to allow Xhaka more freedom to join the left sided attack and replace that with greater defensive attention to Liverpool's top-heavy team and a bit of extra protection for Gabriel.
With Tierney on the bench there's the option of a big tactical pivot later in the match …
Kinda encouraged by the change, it suggests a fair bit of Liverpool-specific preparation has been done.
