Chelsea Football Club needed an extra-time goal from Marcos Alonso to trash League One Plymouth Argyle 2-1 and avoid an FA Cup fourth-round shock.
Plymouth Argyle stunned Stamford Bridge in the eighth minute, going in front when Macaulay Gillesphey found space in the box to nod Jordan Houghton’s free-kick past Kepa Arrizabalaga.
Kovacic rattled the woodwork twice before the Blues equalised shortly before half-time when Captain Cesar Azpilicueta flicked Mason Mount’s low cross in after a slick team move.
The Spaniard had the ball in the back of the net again, but saw the flag go up for offside and Chelsea were unable to seal victory inside 90 minutes, forcing extra time.
Chelsea finally went ahead in first-half extra time with Marcos Alonso popping up to steer Timo Werner’s cut-back into the bottom corner and win the tie for the hosts.