Alvaro Morata scored a stoppage-time winner as Chelsea booked their place in the Carabao Cup semi-finals with a 2-1 win over Bournemouth.
Willian's early goal looked like it would be enough to send Antonio Conte's side through at Stamford Bridge on Wednesday night, but Dan Gosling struck in the 90th minute to level the tie with a fine curling effort.
Antonio Conte named a much-changed XI from the side that beat Southampton at the weekend. Gary Cahill, Willian and Pedro were the only three to keep their places, while youngster Ethan Ampadu and Michy Batshuayi were handed starts.
Bournemouth changed seven, with Steve Cook, Harry Arter and Dan Gosling among those receiving recalls.
It appeared as though the game would be heading for extra time, but substitute Morata popped up in the first of four added minutes to poke the ball home and seal the win.
Chelsea will now face Arsenal in the last four, with the first leg of the tie to be played at Stamford Bridge in January.
Chelsea were the brighter side from the off and a fine team move after 13 minutes saw them open the scoring. Michy Batshuayi and Kenedy combined well before the latter found Cesc Fabregas, and he charged into the box and squared for Willian, who had the simplest of tasks in stroking the ball into an empty net.
Bournemouth suffered another blow immediately after the goal as Jermain Defoe was forced off injured, with Eddie Howe opting to throw on Jordon Ibe in his place instead of a conventional striker, meaning the Cherries largely lacked a focal point throughout the rest of the first half.
Chelsea: Caballero (6), Rudiger (6), Ampadu (7), Cahill (6), Zappacosta (5), Drinkwater (6), Fabregas (6), Kenedy (7), Willian (7), Pedro (6), Batshuayi (5)
Subs: Bakayoko (n/a), Hazard (7), Morata (7)
Bournemouth: Boruc (5), Smith (5), Francis (5), Cook (6), Simpson (6), Surman (5), Arter (5), Gosling (7), Mousset (4), Fraser (6), Defoe (n/a)
Subs: Cook (n/a), Ibe (6), Wilson (n/a)
Man of the match: Ethan Ampadu
Batshuayi may have played a key role in Chelsea's goal, but overall it was a disappointing night for the striker on his chance to impress. There were several occasions where he found himself with the ball at his feet in the box, but could never capitalise and was eventually replaced by Morata.
And it was the Spaniard who scored the winner for Chelsea just a minute after Gosling had pulled Bournemouth level, poking home past Artur Boruc after his fellow substitute Eden Hazard and broken through and played him in.
Man of the match - Ethan Ampadu
Making just his second start for Chelsea, the 17-year-old got over a nervy start which saw him booked for a foul on Jermain Defoe to put in a composed display at the heart of their defence. It was a performance that deserved a clean sheet.
Antonio Conte: "The most important thing is we're in the semi-finals. Last season we lost to West Ham in the second round so we must be happy with this achievement.
"To reach the semi-final in one of the two cups in England is great for us, especially with a lot [squad] rotation. I had good responses from my players and I hope to continue in this way. Many players had their chances tonight to play from the start and I think I had good responses.
"It's also not simple when you concede a goal in the last minute of the game, so to have this type of reaction shows great character, personality and heart."
Eddie Howe: "It feels heartbreaking to be honest. I thought the players gave everything to get back into the game tonight. We didn't get a great start and they scored a good goal from their perspective, but second half we penned them in with waves of attacks and scored a great goal.
"I was hoping it would go into extra-time, but obviously it didn't happen and the last part of the game was bitterly disappointing."
Both sides are back in Premier League action on Saturday, with Chelsea facing Everton and Goodison Park in a match which is live on Sky Sports Premier League, while Bournemouth visit Manchester City.