Chelsea laboured to an unconvincing FA Cup win over Scunthorpe as they overcame the shock of falling behind.
The Premiership leaders were rocked when Paul Hayes turned to fire the Iron into a deserved early lead.
Mateja Kezman levelled with a thumping volley before half-time, and Chelsea went ahead when Andy Crosby deflected Didier Drogba's cross into his own net.
Scunthorpe's Cleveland Taylor header found the post before Eidur Gudjohnsen sealed victory four minutes from time.
The visitors stunned Chelsea when they became only the fourth team to score at Stamford Bridge this season.
Matt Sparrow's low cross found Hayes and Scunthorpe's leading scorer rolled his marker Alexei Smertin to fire through Carlo Cudicini's legs from 12 yards.
Chelsea equalised somewhat against the run of play on 26 minutes when Andy Butler's defensive header fell for Kezman who thumped a 20-yard volley past Paul Musselwhite.
But two minutes later the Premiership leaders switched off again at a corner and Cudicini reacted sharply to claw away Andy Butler's header.
Chelsea were more determined after half-time and after a spell of pressure took the lead, albeit with a dose of good fortune when skipper Crosby was unable to avoid the ball as Drogba swept in a low cross.
But Scunthorpe refused to buckle and had the Premiership leaders sweating on their narrow lead.
Substitute Taylor wasted a golden chance by firing wide from 12 yards with only Cudicini to beat.
Crosby missed an even better chance to make amends when Cudicini misjudged Peter Beagrie's cross, but from three yards out the Iron skipper volleyed into the side netting.
Chelsea were counting their fortune 15 minutes from time when Taylor rose to thump a header against the post.
Their luck held and Chelsea sealed victory four minutes from time when Gudjohnsen was on hand to score from close range after Sunthorpe keeper Paul Musselwhite found Arjen Robben's shot too hot to hold.
Chelsea boss Jose Mourinho:
"I didn't have a very strong defensive line-up. Only Glen Johnson was a regular as a right-back.
"It was the first game for centre-half Steven Watt and the first for Alexei Smertin as a centre-back.
"It was also the first game for Nuno Morais, who is not a left-back, he is a midfielder. But I am very happy with their performances."
Scunthorpe boss Brian Laws:
"I am very proud of the players but a little disappointed we didn't get anything more out of the game.
"We had our chances to equalise. Cleveland Taylor had a volley brilliantly saved by their goalkeeper and then he hit the post.
"We were pressing for the equaliser and then the third goal killed us. But overall, the players did the town, the fans and the club proud - I could not have asked for any more from them."
Chelsea: Cudicini, Johnson, Watt, Nuno Morais, Smertin, Cole,Tiago, Geremi (Paulo Ferreira 69), Gudjohnsen,Kezman (Robben 81), Drogba (Jarosik 68).Subs Not Used: Pidgeley, Grant.
Goals: Kezman 26, Crosby 58 og, Gudjohnsen 86.
Scunthorpe: Musselwhite, Byrne, Crosby, Butler, Ridley,Sparrow, Baraclough, Kell, Beagrie (Williams 90), Hayes,Rankine (Taylor 68).Subs Not Used: Evans, Jackson, Parton.
Goals: Hayes 8.
Ref: D Gallagher (Oxfordshire).