Bayern have yet to taste defeat in the German top flight this term and head to the Coface Arena aiming to finish the first half of the season with that record still intact.
Pep Guardiola's men, who are already 11 points clear at the top of the table, will be heavy favourites to claim three points against a Mainz side with just three league wins to their name.
However, Bayern will have to cope without midfielder Alonso and star striker Lewandowski after both picked up knocks in the 2-0 win over Freiburg on Tuesday.
The duo will be sidelined together with defender Mehdi Benatia, who was already a confirmed absentee, and midfielder Sebastian Rode.
"Benatia, Alonso and Lewandowski won't be on board," Guardiola said. "Rode is sick."
Regardless of the result versus Mainz, Bayern are sure to hold a healthy lead at the summit going into the mid-season break.
However, Guardiola is refusing to take anything for granted and highlighted the struggles of Borussia Dortmund, who sit 16th after finishing second in each of the last two seasons, as an example to heed.
"Just because we were strong in the first half of this season doesn't mean that we will be in the second half," he added.
"It can happen that we lose one or more games. You can see it in Dortmund. Borussia is a super team with a great coach. But if it can happen to them, then it can to us."
