What was already a big match became a monumental affair due to the fact that it represented the final home match for Ruben Amorim in charge of Sporting, with the 39-year-old set to become the new Manchester United manager next week.
Amorim will officially move to the Red Devils on November 11, with his first game in charge set to be the Premier League game against Ipswich Town on November 24, and the Portuguese has a huge job on his hands at Old Trafford.
Man United have once again desperately underperformed this season, but they are hoping that Amorim will be the head coach to change their fortunes, and it will be fascinating to see how he fares in Manchester.
Here, Sports Mole discusses why Man United fans should be excited about Amorim's arrival, having guided Sporting to a standout victory over the reigning Premier League champions.
Half-time motivation: How Sporting turned the game against Man City
Sporting found it difficult for long stages of the first half against Man City, with Foden making the breakthrough, and it did appear that the English champions would go on to win the match with relative ease.
However, Gyokeres made it 1-1 late in the first period before Sporting scored twice in the early stages of the second half to make it 3-1, with Man City shocked by the Portuguese outfit's tempo immediately after the half-time break.
What was said in the dressing room has not been disclosed, but it worked, with Amorim motivating his side.
A fourth came in the 80th minute from Gyokeres; Man City just could not live with Sporting in the second half, and it was the type of performance that would have made Man United fans take notice.
There were huge question marks over Erik ten Hag's ability to motivate his players, but Amorim has the look of a head coach that commands respect, and his motivational words helped turn the game in Lisbon.
Amorim tactics: A back three or a back five?
Amorim said after the match that he would not be able to fully implement his playing style at Sporting when he takes charge of Man United, insisting that he "will have to adapt" when he moves to the 20-time English champions.
"I already said previously you cannot transport one reality into another. At Manchester United you cannot play exactly like this. You cannot play so defensively and so there we will have to adapt. Clearly it is really difficult to beat this team and to beat Pep Guardiola. And he is not a worse manager than me," he told reporters.
"It will be a completely different world, a different team, we won't have that much time to train and we will begin from a different starting point. People can make their own judgements but I say to the people of Manchester that this was a one-off."
Amorim famously sets his team up in a back three, but Sporting were often in a back five against Man City, with the English giants arguably the best side in world football in possession of the ball.
It remains too be seen whether Amorim sticks with a back four or changes the system entirely, with much depending on which players are available; Leny Yoro and Luke Shaw could both be vital in the new set-up, but both are currently on the sidelines.
Geovany Quenda and Maximiliano Araujo were outstanding as the wing-backs against Man City, and the role could suit Diogo Dalot, but it will be a big risk to attempt to completely change the system at this stage of the season.
Gyokeres looks the real deal: Could Man United sign him?
A lot is asked of Gyokeres in this Sporting team, but he looks to be the real deal, with the 26-year-old scoring 23 goals and registering four assists in 17 appearances during the 2024-25 campaign.
Gyokeres has now scored seven times in his last two appearances, including his hat trick against Man City, while he has 66 goals and 19 assists in 67 appearances for the Green and Whites in all competitions.
The Sweden international is currently being heavily linked with a move to Man United, and Amorim has suggested that he will be on the move at the end of the season, with the Red Devils likely to be in the mix to sign him.
"If I start joking about this Gyokeres situation I'll get in trouble," Amorim told reporters. "This is my city, this is my country, so I'll respect it. Viktor has to stay until the end of the season and then his life will probably go somewhere else."
Man United fans will also be hoping that Amorim can improve Rasmus Hojlund in a similar way, as the Denmark international certainly has the capabilities to thrive in the head coach's new system with a little more guidance.
Result against Man City was a statement
It remains to be seen whether Amorim is a success at Man United, but Tuesday's stunning result against Man City would have sent out a serious statement to the team's rivals in the Premier League.
It was a Man City without some key players and struggling for a bit of form, but it was still the reigning English champions, and Sporting had too much for them in the second half of the contest.
Amorim looks to have the charisma required to be in charge of Man United, and he will be looking to make it eight straight wins in all competitions in his final game as Sporting manager against Braga this weekend.
The head coach will be leaving Sporting in excellent shape, with the Green and Whites looking capable of having a brilliant season, and Man United fans will be hoping that can translate into success at Old Trafford.