"It was a high cross, I thought everything was alright but didn't see the striker coming close to me then I dropped the ball," Cerny to the Spurs website. "Afterwards I felt very bad, especially as it was in my home town.
"Every player makes a mistake but I go home, play my old club and make a mistake - so I'm disappointed. It happens in football, sometimes it's like this. Still, we won the game and that's the most important thing.
"In the first half we had good combination play from back to front, scored two goals and played great football but in the second half I made the mistake and Slavia played a little differently, switched to 4-4-2 and we couldn't pass it like we did in the first half.
"We won but we weren't happy about the result because we could have scored more goals. Now we have to concentrate 100 per cent on the return leg. Slavia continue their league programme this weekend and we have to be ready."