Tottenham beat Chelsea 5-4 on penalties to reach the Carabao Cup quarter-finals after Erik Lamela's 83rd-minute equaliser saw the game end in a 1-1 draw.
Chelsea went ahead after 19 minutes in a positive first half for them, with Timo Werner scoring his first goal for the club since his summer move, powering an effort past Hugo Lloris.
But Tottenham were vastly improved after the break and deserved their equaliser as Lamela swept home from debutant Sergio Reguilon's cross with just seven minutes to play, sending the game to a penalty shootout.
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With the first nine players stepping up to score, it fell to Mason Mount for the visitors' fifth spot-kick but he pinged his effort wide off the crossbar, knocking Chelsea out despite leading the game for 83 minutes, and sending Tottenham into the quarter-finals.
How Spurs came from behind to beat Chelsea
Chelsea began brightly and made it count when Werner put the visitors ahead. Tottenham debutant Reguilon was beaten far too easily by his fellow Spaniard Cesar Azpilicueta down the right flank, with the Chelsea captain cutting the ball back for Werner at the top of the area. The striker set himself up perfectly before firing a powerful effort into the bottom corner.
Tottenham: Lloris (7), Alderweireld (7), Dier (8), Tanganga (6), Aurier (7), Gedson (6), Ndombele (6), Sissoko (7), Reguilon (7), Bergwijn (6), Lamela (7).
Subs used: Hojbjerg (6), Kane (6), Moura (6).
Chelsea: Mendy (7), Azpilicueta (7), Zouma (7), Tomori (6), Chilwell (7), Jorginho (7), Kovacic (7), Hudson-Odoi (6), Mount (7), Werner (7), Giroud (6).
Subs used: Emerson (5), Kante (6), Abraham (6).
Man of the match: Eric Dier
Despite offering little in attack up to that point, Tottenham could have snuck home the equaliser just after. Gedson Fernandes pounced on a loose ball before driving into the area, but Kurt Zouma came across to make a well-time tackle - aided by new Chelsea goalkeeper Edouard Mendy. Their efforts saw the ball run away from Fernandes as he struggled to get back to his feet amid the tangle.
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Mendy showed more of what he could do with 10 minutes of the half to play. Lamela turned well past Jorginho before striking, but the goalkeeper got down low to push the ball away with his foot. He then came out to collect a looping clearance from Fikayo Tomori.
It must have been some half-time team talk from Jose Mourinho as Tottenham were vastly improved after the break. Steven Bergwijn fired a warning shot inside four minutes as he lifted an effort over the crossbar. But the pick of the early chances came when debutant went up against debutant as Mendy palmed away a powerful effort from Reguilon at the near post.
- Sergio Reguilon made his Tottenham debut Mourinho made wholesale changes from the 1-1 draw with Newcastle. Only Hugo Lloris and Eric Dier kept their places.
- There was also a Chelsea debut with goalkeeper Edouard Mendy in the XI. Ben Chilwell also made his first start at left-back while only Mateo Kovacic, Mason Mount and Timo Werner kept their places from the side that drew 3-3 at West Brom.
The new Spurs signing then nodded wide as the half chances kept coming for both sides before Werner attempted to added a second to his tally but could only send a low drive straight into Lloris' hands. Callum Hudson-Odoi and substitute Harry Kane both skied efforts into the empty stands before Tottenham snatched a deserved equaliser.
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Reguilon was involved in the attacking play once again, picking out Lamela towards the back post with a wonderful, floated cross. It was then an ultimately easy slotted finish from the midfielder with Emerson - who had replaced Ben Chilwell - unable to stop Lamela turning home.
With neither side able to find another in the final 10 minutes or so, the game was sent to penalties - quite the moment for Mendy on his debut. However, he was unable to be Chelsea's hero on the night with Tottenham scoring all five of their spot kicks.
It then fell to 21-year-old Mount to send the shootout to sudden death, but he pinged his kick onto the crossbar before it flew wide, sealing Chelsea's exit from the Carabao Cup.
Man of the match - Eric Dier
Dier was one of only two players to keep their places from the draw with Newcastle just over 48 hours ago and showed no ill effects after being controversially penalised for handball late in the game.
He completed 42 of his 48 passes at a rate of 87.5 per cent and made four clearances as Tottenham recovered from a slow start.
Dier was praised by his manager after the game with Jose Mourinho telling Sky Sports: "What Eric Dier did is not normal and I have to praise him in a special way. The football authorities have so many rules at the moment but it should be forbidden for a player to play two matches at this intensity in 48 hours.
"The Newcastle match was a Premier League match, and this one was a match at Premier League level. It is not human what Eric Dier did."
There was also a comical call of nature for Dier as he sped off down the tunnel in the second half - pursued by a storming Mourinho - but he soon came back out to finish the game and score in the penalty shootout
The manager added: "He had to go! But I was just trying to put pressure on him to have him back for the rest of the game. He was a great example for everybody playing these two matches."
Tottenham head coach Jose Mourinho said: "I told you before the game we would be ready to fight and we were ready to fight. I told the players before the penalties that I don't care about the penalties, I care about what we did before.
"We were the best team, we were magnificent. In the second half a super team like Chelsea looked very ordinary, and they are not. We played so, so well.
"I told the players they should only think about this game, but I have to think about three games at the same time. They only thought about this game and they were phenomenal, so all credit to the boys.
"I have an incredibly negative record on penalty shootouts, but today I had a feeling that everything was going well. We were by far the best team and the boys deserved to win the match."
Chelsea head coach Frank Lampard said: "You get to penalties and anything can happen at that stage. You want to stay in these competitions of course, but there was some really good bits in our performance.
"The first half was as dominant as you can get in terms of possession. You want to create more chances, yes, but Tottenham were out of of the game. In the second half, they messed our game up a bit, but with the control we had before then we wanted to score more goals or that can happen.
"When teams go long and miss your press and turn you round the other way it's not easy to get the fluidity and rhythm going. It was a clear change of tactic from them, and it's something we need to deal better with.
"We looked tired at the end which was understandable given where we are at. Timo Werner had some cramping at the end so he didn't take a penalty."
How did Mendy and Reguilon fare on their debuts?
Analysis by Sky Sports journalist Charlotte Marsh:
"It was ultimately a good debut from Mendy. The 28-year-old has been bought in to solve a goalkeeping problem and looked assured in a Chelsea shirt. In the first half, he did well to come out and help smother Fernandes' run and his first save from a set-piece was a strong punch.
"As Tottenham began to test him more, Mendy was equal to the challenge, denying Lamela and Reguilon. There was one nervy moment in the second half when he failed to claim a corner, but a strong collection not long after dampened those fears.
"He will have been disappointed with the result and conceding late on, but that asked more questions of Emerson than the goalkeeper. Overall, it was a confident performance and he may have even booked a spot in the starting line-up against Crystal Palace on Saturday.
"On the other side, it was a zero to hero performance from Reguilon on his Tottenham debut. He took a while to settle into the game and was given the slip all too easily by Azpilicueta in the build-up to Chelsea's goal.
"But after that - and particularly in the second half - the left-back was incredibly impressive. As Spurs moved further forward, Reguilon became dangerous on the left wing and twice went close himself, being denied by Mendy's foot and nodding wide not long after.
"It was his sweeping cross for Lamela's equaliser that will really have caught the eye and excited Tottenham fans. While he may need a little bit of shoring up in his defensive duties - which will come with time and adaptation to the Premier League - he showed bags of potential on his first outing."
- Jose Mourinho has progressed from 26 of his 31 League Cup ties, with this the first time he has ever progressed via a penalty shootout in the competition, losing his previous three.
- Jose Mourinho has faced Frank Lampard four times without winning in his managerial career (D2 L2) - twice as many as he has faced any other manager without registering at least one win.
- Only Robert Lewandowski (56), Ciro Immobile and Cristiano Ronaldo (40 each) have score more goals among players in Europe's top five leagues in all competitions since August 2019 than Timo Werner (35).
- Erik Lamela has been directly involved in six goals in his last four League Cup starts for Tottenham (3 goals, 3 assists).
It is a quick turnaround for Tottenham, who will host Maccabi Haifa in their Europa League play-off match on Thursday (kick-off 8pm), before travelling to Jose Mourinho's former side Manchester United in the Premier League on Sunday, live on Sky Sports (kick-off 4.30pm).
For Chelsea, they are back in Premier League action on Saturday when they host Crystal Palace (kick-off 12.30pm).