Oscar scored the only goal of the game in the final 10 minutes to give the Blues a first-leg victory in their last-32 tie.
© PA Photos
The best chance of the first half eventually fell to David Lafata on 30 minutes, but the striker fluffed his lines and put his shot wide.
© AP Photos
If both teams showed plenty of attacking intent in the opening 45 minutes, the second period saw little action in front of goal.
Cech easily gathered Krejci's long-range drive, while Lampard's tame header posed no problem for Vaclik.
However, Chelsea finally made the breakthrough on 82 minutes when Oscar, who had only been on the pitch for a minute, slotted home following an exchange of passes with Eden Hazard.