Valencia host Chelsea in a Champions League Group E blockbuster on Wednesday, while Leverkusen will look to find form against Genk.
Chelsea's visit to the Mestalla will be notable for the return of midfielder Juan Mata to Valencia, the club which he left a month ago after a reported 30-million-euro switch to the London giants.
Mata has sparkled in the short time at Stamford Bridge, adding new energy to a Chelsea midfield that has at times been criticized for looking too stagnant.
He has scored twice for his new club, including a late strike in Chelsea's 2-0 win over Leverkusen in their Champions League opener a fortnight ago.
Chelsea face a Valencia side who have not lost at home this season in all competitions.
The Spaniards have conceded just six goals in their five La Liga matches and began the group stage with a scoreless draw against Genk.
They will look to build on that against Andre Villas-Boas' side and will hope the free-scoring Roberto Soldado, who has struck five times in La Liga this season, can breach Chelsea's defence.
A 1-0 defeat at Sevilla on Sunday will give Valencia the motivation to respond, while Chelsea will hope to continue on from their 4-1 win over Premier League newcomers Swansea City on Saturday.
Fernando Torres, who scored the opener but was then sent off for a straight red card in that match, is eligible to play and has impressed in recent weeks.
Brazilian midfielder Ramires, who netted a brace against Swansea, is also in form and seems to be thriving under Chelsea's new Portuguese manager.
Leverkusen need to bounce back from a poor run of form as they entertain Belgian champions Genk, with last season's Bundesliga runners-up having dropped three games in a row.
A 4-1 defeat to local rivals Cologne in their last home fixture started the rot, while Bayern Munich showed the gulf in class when they cruised to a 3-0 victory at the Allianz Arena against Robin Dutt's side on Sunday.
Genk will fancy their chances at the BayArena, with the Belgian First Division outfit on an unbeaten run of seven matches in all competitions.
Mario Been's side highlighted they have the defensive capabilities to compete in Europe during their clash with Valencia, while 12 goals in their last three domestic outings indicate that the Belgians are also potent up front.