Chelsea suffered an FA Cup fourth-round scare on Saturday when they had to come from behind and needed extra time and a penalty save to beat League One Plymouth Argyle 2-1 with goals from Spaniards Cesar Azpilicueta and Marcos Alonso.
Plymouth shocked the Premier League side when defender Macaulay Gillesphey nodded the ball home from a free kick by former Chelsea player Jordan Houghton in the eighth minute, sparking wild celebration and a shower of green balloons from the travelling fans.
Chelsea coach Thomas Tuchel had tested positive for COVID-19 and missed the game. It was not clear whether he would be free to travel to Abu Dhabi next week for the Club World Cup.
His expensively assembled squad looked rusty and heavy-footed after a fortnight's break and though they had more than 40 shots, their performance was well below their best.
Striker Romelu Lukaku failed to take command up front and rarely looked like scoring.
Chelsea hit the woodwork three times in the first half, twice through Mateo Kovacic and again through Callum Hudson-Odoi but Plymouth's well drilled defence kept the European champions at bay until the 41st minute when quality told.
Captain Azpilicueta scored with a neat backheel from a low Mason Mount cross.
Plymouth absorbed waves of Chelsea attacks in the second half and extra time and last-ditch defending as well as inspired goalkeeping from Mike Cooper kept the hosts out until the 16th minute of extra time.
Alonso broke the deadlock when he got on the end of a pass from Kai Havertz and swept the ball in.
With five minutes to go Plymouth earned a penalty when Malang Sarr brought down Ryan Hardie in the box.
But Plymouth joy was short-lived when Spain's Kepa Arrizabalaga dived low to his left to save Hardie's shot.