Pedro's smart double helped Chelsea ride out a worrying wobble to see off Slavia Prague 4-3 and reach the Europa League semi-finals.
The Blues won their quarter-final 5-3 on aggregate, but at a push rather than a canter, squandering a 3-0 lead in Thursday's second leg at Stamford Bridge.
Pedro opened the scoring after only five minutes and, after Simon Deli's own goal, the Spaniard teed up Europa League top-scorer Olivier Giroud for his 10th of the competition.
Tomas Soucek headed home unmarked for Slavia before the break, only for Pedro to score the fifth goal of the match before the half-hour mark.
After the interval Petr Sevcik blasted home two long-range strikes in three minutes to give Slavia hope of an unlikely comeback, but there was to be no Chelsea collapse.
The Blues became just the second Premier League team after Manchester City to hit 100 goals in all competitions this term, but slipped woefully off the pace after building a commanding lead.
Maurizio Sarri stalked the touchline with a mixture of panic and fury for the last quarter-hour, dispensing entirely with his technical area as his emotions ran unchecked.
The head coach can be forgiven for expecting a cakewalk conclusion, especially after Chelsea raced into that 3-0 lead inside 20 minutes.
Pedro exchanged passes with first Cesar Azpilicueta and then Giroud, before lashing home a stylish opener.
The Spaniard nearly scored again three minutes later, turning Hazard's low cross against a post, only for the rebound to strike defender Deli in the head and bounce over the line.
If that own goal proved cruel, N'Golo Kante's through-ball for Chelsea's third was exquisite. Pedro raced on to the defence-splitting pass, squared to Giroud and the France striker tapped home.
A semi-final berth seemingly already assured, Chelsea switched off long enough for Slavia skipper Soucek to nod home unmarked from a corner.
Chelsea hit back immediately, though, Pedro scuffing home his second and the Blues' fourth.
The hosts' dominance evaporated at the top of the second half, Sevcik twice netting from distance to shock the Blues.
Goalkeeper Kepa Arrizabalaga should have reached the first but could do little about the second, a thunderbolt to shake Stamford Bridge and change the mood entirely.
Suddenly the Blues' cruise was under threat. And had Sevcik connected in the box when he slipped instead, their last-four place could have come under serious threat.
David Luiz got away with a cynical handball to deny Slavia a late chance, with the visitors squandering their free-kick on the edge of the Chelsea area.
And so the Blues held out, surviving a genuine fright when they should have breezed through.