Sporting stole the show with their performance in Lisbon, but the Portuguese champions had to come from behind after Phil Foden put City ahead early on.
Amorim was hoping to sign off from the Champions League in style as Sporting coach before he leaves for Manchester United, and Gyokeres then took centre stage.
The Swedish striker equalised seven minutes before half-time, holding off Champions League debutant Jahmai Simpson-Pusey as he ran through to finish.
Sporting then went ahead 19 seconds into the second half as Maximiliano Araujo finished off a fine move, and shortly after that Gyokeres converted a penalty following a foul by Josko Gvardiol.
City could have pulled one back, but Erling Haaland hit the bar from the spot. Gyokeres showed Haaland how to do it as he scored his second spot-kick to complete a hat-trick, condemning City to their heaviest losing margin in Europe since a 3-0 loss to Liverpool in April 2018.
Gyokeres has 23 goals in 17 games in all competitions this season and will surely be the next star to leave Sporting for a bigger club elsewhere following Amorim’s departure.
“It was written that it had to be like that I think, there is no other explanation,” Amorim, at Sporting since 2020, said of a famous victory.
“I think everyone who has been here in the last four years deserved this. It was a special night.”
Diaz hat-trick
City have seven points at the halfway stage in the new-look Champions League, while Sporting are second on 10 points, behind only Liverpool, who are the sole team with the maximum 12 points.
Luis Diaz scored a hat-trick as the Anfield club secured a statement 4-0 win over Leverkusen on the night Alonso returned to Merseyside, with all the goals coming in the second half.
Diaz put Liverpool ahead just after the hour mark and Cody Gakpo headed in shortly after. Diaz scored again to make it 3-0 and then got his third and his team’s fourth in stoppage time, leaving the German champions on seven points after four outings.
“I think it’s a good result against a very good team,” Gakpo told Amazon Prime.
“They played a very good game, but we kept going, trying, creating chances, defending well.”
Real slump again
Madrid suffered their second loss in four games in the competition this season as they went down 3-1 at home to Milan.
The Italians, whose tally of seven European Cups is bettered only by Real’s 15, went ahead early on through Malick Thiaw, but the hosts soon drew level through a Vinicius Junior penalty.
However, Alvaro Morata put Milan back ahead before the interval against his old club, following in to finish after a Rafael Leao shot was parried.
Milan got their third on 73 minutes after great play by Leao set up Tijjani Reijnders to score, and Antonio Ruediger had a late effort disallowed for Real.
“When we are 11 lions on the pitch, it is very difficult for a team to beat us,” Morata said at full-time.
Monaco are third in the standings with 10 points following a 1-0 victory at Bologna, secured thanks to captain Thilo Kehrer’s late goal.
Dortmund are fourth on nine points after Donyell Malen’s 85th-minute goal gave them a 1-0 win at home to Sturm Graz.
Dusan Vlahovic’s penalty allowed Juventus to come from behind and draw 1-1 at Lille, after Canada’s Jonathan David had given the French side the lead.
Celtic impress
Celtic have seven points after a fine fightback secured a 3-1 win for the Scottish champions against RB Leipzig in Glasgow.
Christoph Baumgartner fired Leipzig in front but a brilliant Nicolas Kuehn strike brought Celtic level and he then put them ahead in first-half stoppage time. Reo Hatate got their third.
PSV Eindhoven crushed Girona 4-0, with Ryan Flamingo and Malik Tillman netting in the first half. Arnau Martinez was sent off for Girona before Johan Bakayoko made it 3-0 and Ladislav Krejci scored an own goal.
Dinamo Zagreb came back to win 4-1 at Slovan Bratislava with Sandro Kulenovic scoring twice for the Croatians.
Slovan, Sturm Graz and Leipzig have lost four out of four.
AFP
