Marcos Alonso struck late to give Chelsea a precious lead in their Europa League quarter-final.
The Blues were frustrated throughout with Willian going close after rattling the crossbar with a thunderous hit from the edge of the area.
Kepa Arrizabalaga was forced into action on numerous occasions and made a fine save to deny Ibrahim Traore from range.
The Spaniard pulled off another fine save to deny Jan Boril from close range.
And after surviving pressure from the hosts, Alonso hit a late winner to secure the lead heading back to Stamford Bridge.
Chelsea play Liverpool on Sunday in a crucial match that will determine who will win the Premier League and who will finish inside the top four.
