Leverkusen won 3-1 away to Hoffenheim, while Mainz defeated Augsburg by the same scoreline.
Match preview
Indeed, after losing each of their previous two matches to fall back into the bottom half of the table, Xabi Alonso would have been relieved to see his side sweep aside Hoffenheim on the road last time out in the Bundesliga.
Robert Andrich provided the visitors with the perfect start by breaking the deadlock after only six minutes, before Moussa Diaby doubled Leverkusen's lead just two minutes into the second half. Nine minutes later, Adam Hlozek ensured his side would be returning home with all three points secured before Stanley Nsoki's late consolation goal.
Die Werkself suffered a major setback in the Europa League in midweek, though, as they lost 3-2 at home to Monaco in the first leg of their play-off tie. Second half strikes from Diaby and Florian Wirtz had turned the game on its head after Lukas Hradecky's early own goal, but an injury time effort from Axel Disasi saw the French side return to the principality with a vital lead to hold onto after Krepin Diatta had equalised.
Ahead of their trip to the south of France on Thursday, Alonso will be determined to see his side rebuild confidence by securing a second successive league victory against Mainz at BayArena on Sunday.
Mainz, on the other hand, will benefit from having eight days between fixtures, and as a result Bo Svensson's side may sense a great opportunity to inflict a minor upset against their more illustrious opponents.
Die Nullfunfer secured a hugely significant 3-1 win against Augsburg last weekend, with a Lee Jae-Sung brace coming either side of Karim Onisiwo's strike to move their side five points clear of Augsburg in the table, despite the two teams only being separated by one position.
With Hertha Berlin nine points back in the relegation play-off spot ahead of this weekend's action, Mainz look set to secure their safety for yet another season, having remained in Germany's top flight since their last promotion in 2009.
Svensson's side have collected an equal share of points at home and on the road during this campaign, too, further strengthening their chances of claiming a positive result against Leverkusen on Sunday.
Bayer Leverkusen Bundesliga form:
W
W
W
L
L
W
Bayer Leverkusen form (all competitions):
W
W
L
L
W
L
Mainz 05 Bundesliga form:
D
D
L
W
L
W
Mainz 05 form (all competitions):
D
L
W
L
L
W
Team News
Leverkusen will remain without Charles Aranguiz and Andrey Lunev due to calf and back injuries respectively, while Diaby is a doubt after being withdrawn during the second half of his side's defeat against Monaco on Thursday.
The talented winger appeared to tweak a muscle and he is therefore unlikely to be risked ahead of the second leg later this week, with Callum Hudson-Odoi and Amine Adli representing potential replacements against Mainz.
Mainz, meanwhile, will travel without Jonathan Burkardt and Delano Burgzorg due to knee and ankle issues respectively, while Robin Zentner, Marlon Mustapha and club captain Silvan Widmer are all significant injury doubts themselves.
As such, Svensson's only change may be to reintegrate Dominik Kohr to his starting XI after the midfielder sat out his side's win against Augsburg following a minor injury from their previous match.
Bayer Leverkusen possible starting lineup:
Hradecky; Tapsoba, Tah, Hincapie; Frimpong, Demirbay, Andrich, Sinkgraven; Hlozek, Wirtz, Hudson-Odoi
Mainz 05 possible starting lineup:
Dahmen; Hanche-Olsen, Bell, Fernandes; Da Costa, Barreiro, Kohr, Caci; Lee; Onisiwo; Ajorque
We say: Bayer Leverkusen 1-1 Mainz 05
With Leverkusen losing to Monaco less than 72 hours prior to kicking-off against Mainz on Sunday, we believe the visitors can claim a positive result at the BayArena.
Svensson's side have been decent away from home this season, with their front three undoubtedly capable of causing the hosts significant issues in transition. Both teams may settle for a share of the spoils should the match be heading in that direction.