Mason Mount missed the crucial spot-kick as Tottenham edged past Chelsea on penalties after a 1-1 draw to reach the Carabao Cup quarter-finals.
A total of nine penalties had been converted before Mount stepped up to take the 10th, but the England midfielder's effort clipped the post and went wide.
Chelsea had dominated the first half and new signing Timo Werner netted his first goal for the club with a clinical finish into the bottom corner.
Spurs responded well after the break and debutant Sergio Reguilon's side-footed effort from inside the area was pushed over the crossbar by Chelsea goalkeeper Edouard Mendy, who was also making his first appearance for his new club.
Jose Mourinho's side got their rewards seven minutes from time when Spaniard Reguilon's cross sailed through to the back post for Erik Lamela to coolly convert from six yards.
With no extra time played, the match went straight to penalties and Mount was the only player to miss.