Cesc Fabregas made an emphatic point to Chelsea manager Antonio Conte as his double sealed a 4-2 win at Leicester, while Everton and Bournemouth suffered shock third-round exits from the English Football League Cup on Tuesday.
Fabregas has been limited to three substitute appearances in the Premier League since Conte took charge over the summer, but the Spain midfielder proved he can still be a game-changer with an influential display capped by the decisive two goals in extra-time.
"I was happy to play from the start! Hopefully this will shut up a few journalists talking rubbish all the time," said Fabregas, who has been linked with a move away from Chelsea.
Elsewhere, second-tier Norwich spoiled Everton's impressive start to the season and inflicted Ronald Koeman's first defeat as Toffees boss with a 2-0 win at Goodison Park.
Bournemouth were the other top-flight casualties as second-tier Preston won 3-2 thanks to a hat-trick from Denmark striker Simon Makienok.
At the King Power Stadium, Shinji Okazaki put Premier League champions Leicester ahead in the 17th minute when the Japan striker punished terrible Chelsea defending to head home from close range.
Okazaki followed his first goal since March with a second in the 34th minute.
Gary Cahill reduced the deficit on the stroke of half-time, the defender heading home after being left unmarked at the far post from a Fabregas corner.
The Blues equalised four minutes after the interval through Cesar Azpilicueta's blistering long-range effort.
Leicester had to play extra-time with 10 men after Marcin Wasilewski's 89th minute dismissal for elbowing Diego Costa and Fabregas made them pay, finishing a flowing move in the 92nd minute and drilling home again two minutes later.
Everton are second in the Premier League but Koeman made six changes and his stand-ins were brushed aside by promotion-chasing Norwich.
The Canaries went ahead when former Everton striker Steven Naismith slipped as he went to shoot and inadvertently lobbed the ball into the net.
Josh Murphy's superb strike from the edge of the area in the 74th minute completed the upset.
"I can't criticise the players. We played well but weren't clinical enough. The difference was Norwich were clinical with their two chances," Koeman said.
At Dean Court, Makienok, who hadn't scored in his previous 19 appearances, gave Preston the lead in the 10th minute before Bournemouth equalised through Lewis Grabban's 53rd minute penalty.
Dan Gosling put the hosts ahead from close range in the 76th minute, only for Makienok to force extra-time in the 85th minute and then win it for Simon Grayson's men in the 111th minute.
Lucas Perez's first goals for Arsenal inspired a 4-0 rout of second-tier Nottingham Forest at the City Ground.
Gunners boss Arsene Wenger, who has never won the League Cup, made 11 changes from the team that thrashed Hull on Saturday and the understudies went ahead in the 23rd minute through a long-range effort from Switzerland midfielder Granit Xhaka.
Spanish striker Perez, who arrived from Deportivo La Coruna on transfer-deadline day, opened his Arsenal account in his third appearance with a 60th-minute penalty after a foul on Chuba Akpom.
Perez got his second in the 71st minute and Alex Oxlade-Chamberlain got Arsenal's fourth in stoppage time.
"It was a motivated team against us and we had a complete performance. The speed and movement of our play was fantastic," Wenger purred.
Liverpool, last year's beaten finalists, remain on course for a return to Wembley after a 3-0 win against Championship side Derby at the iPro Stadium.
Estonia centre-back Ragnar Klavan took advantage of poor Derby defending to fire home in the 24th minute.
Philippe Coutinho doubled Liverpool's lead in the 50th minute and Divock Origi put the result beyond doubt four minutes later.
Newcastle defeated Championship rivals Wolves 2-0, Leeds beat fellow second-tier side Blackburn 1-0, while Reading won 2-1 in another all-Championship clash at Brighton.