Two second-half goals from the visitors made Stamford Bridge uneasy, but Chelsea held on to claim the victory on the night and advance 5-3 on aggregate.
Chelsea’s penchant for complacency at the start of the second half once again reared its ugly head, and that will be a worrying sign for the supporters and manager Maurizio Sarri.
But no one could have anticipated the dramatic finish, not after a first-half performance that was so dominant that you thought Chelsea might be able to take Eden Hazard off after just 45 minutes to rest him.
Pedro opened the scoring just five minutes in when a clever one-two with Olivier Giroud gave him the space inside the penalty area to go one-on-one with Ondrej Kolar and produce a little chip over the stranded goalkeeper.
Just four minutes later, Chelsea had their second. Hazard darted into the penalty area and squared for Pedro on the far post for a tap-in. Pedro’s shot ricocheted off the post and off Simon Deli into the net, giving Chelsea a lead that should have seen them comfortably through the tie.
Chelsea kept attacking. This time, Pedro turned provider on the counter attack when he found himself in acres of space on the right. The Spaniard squared the ball to Olivier Giroud to sweep into the net from the centre of the penalty.
Set pieces have been a problem for Chelsea all season, and Slavia Prague took advantage to pull one back and score a vital away goal. Tomas Soucek found himself unmarked inside the area and stooped to direct a header past Kepa Arrizabalaga.
But Chelsea restored their three-goal lead again through Pedro. Emerson’s cross into the area was attack by Giroud who attempted a back heel. The ball deflected off the striker straight into the path of Pedro who simply poked the ball into the net on the far post.
Slavia Prague looked a different side in the second half as Chelsea started to sit off and take their foot off the gas. Petr Sevcik attempted an ambitious shot from outside the area that seemed to catch Arrizabalaga flat-footed in goal and Sevcik’s shot nestled in the bottom corner of the net.
Minutes later, Sevcik repeated the trick, but this time with a world-class strike. From almost the same position outside the box on the right, Sevcik’s shot this time was fired towards to the top left corner of Arrizabalaga’s goal and beat the Spaniard for pace.
Slavia Prague now had all the momentum and created a number of half-chances to keep Chelsea under pressure, but the hosts clung to that one-goal lead on the night to win the tie and earn the right to play Eintracht Frankfurt in the next round.