Wolfsburg suffered something of a continental hangover after they slumped to a 1-1 draw at Mainz in the Bundesliga on Sunday.
Dieter Hecking's men beat Inter 2-1 away from home on Thursday to claim a 5-2 aggregate triumph and reach the last eight of the UEFA Europa League, but they were far from their best as attentions turned back to domestic action.
Second-placed Wolfsburg found themselves with an uphill struggle after just seven minutes, as Niko Bungert rose above Timm Klose to nod Johannes Geis' fine corner delivery beyond Diego Benaglio in the visitors' goal.
The hosts' positive start almost saw their lead doubled a few moments later, though on this occasion Wolfsburg escaped unscathed, as Stefan Bell headed another Geis corner just over.
Geis remained a considerable threat and he struck the crossbar with a powerful drive just before the half-hour mark, as Mainz continued to dictate proceedings.
In response to his side's poor first-half showing, Hecking introduced Vieirinha and Ivan Perisic for Josuha Guilavogui - handed a call-up to the France squad on Sunday - and Sebastian Jung at the break, with those changes making a significant difference.
Mainz were given a warning after an hour, as Luiz Gustavo robbed Julian Baumgartlinger before firing against the post.
But he was not to be denied a minute later, stabbing home from close range after Naldo flicked on a Kevin De Bruyne corner.
There was to be no later winner, though, with Wolfsburg's slim title hopes suffering a blow.