The right-back, 17 years and 346 days old and making his first senior start, provided the spark for an exceptionally lackluster City on Wednesday when he struck a superb equalizer at the Etihad Stadium.
Rafa Mir had given the Spanish side a surprise lead but City stepped up after Lewis leveled early in the second half and went on to win convincingly with strikes from Julian Alvarez and Riyad Mahrez.
There had been nothing on the game with City already confirmed as Group G winners and Sevilla heading to the Europa League from third place.
Consequently, the first half was a largely forgettable affair, notable only for Mir’s well-taken header.
City generally dominated possession but, amid torrential downpours and a flat atmosphere, they rarely got out of first gear.
It wasn’t because of a lack of star quality. Again Erling Haaland was not put at risk through injury and Kevin De Bruyne was among the players on the bench as Guardiola made seven changes but the line-up was still full of internationals seniors.
Only Lewis, fellow countryman Cole Palmer and goalkeeper Stefan Ortega were not first-team regulars.
City were also given a handful of chances by Sevilla’s unconvincing goalkeeper Yassine Bounou but they were unable to take advantage of them with Palmer firing over and Ilkay Gundogan having an effort blocked.
City were stunned on the half-hour mark as Mir went unmarked at the far post to meet Isco’s corner with a firm header that went past Ortega.
Jack Grealish forced a save from Bounou in response, but it wasn’t until the second half that they found a spark.
It was Lewis who provided it as he completed the latest in a series of runs in Sevilla territory. When the visitors failed to clear, Alvarez played the teenager on goal and he finished like a veteran with a firm shot past Bounou.
City nearly took the lead moments later, but this time Bounou collected a firm header from Ruben Dias under the crossbar.
Guardiola decided to pick up the pace even further by introducing De Bruyne in the 70th minute and within three minutes the Belgian playmaker had created the goal that gave City the lead.
De Bruyne picked out Alvarez with a superb pass behind the defense and the Argentine coolly swerved around Bounou to head home.
Alvarez wasn’t finished there and he set up the third as he stole a Jose Carmona and attacked Mahrez.
City had late chances to add a fourth but Bounou saved from Dias and Phil Foden.
Additional PA Reports