Another former Liverpool favourite Luis Suarez promised not to celebrate if he scored on his former stomping ground, but there was no love lost for the Uruguayan among the home faithful as he was showered with abuse after trying to buy cheap free-kicks.
But Gundogan still reckons Liverpool can cause an upset, and the Germany global told DAZN: "I've already thought about it and somehow I have the feeling that it's not over yet".
Few expected to see the Reds make it to next month's Madrid finale after a 3-0 first-leg defeat at Camp Nou, but the five-time European champions will face Ajax or Tottenham Hotspur after digging deep in stunning fashion.
But Fowler, who came through the club's academy, believes Suarez disrespected Liverpool in the way he left - having previously looked to push through a move to Arsenal a season earlier.
"I was really angry that the manager put me on the bench". All of a sudden people go: "oh, he stayed, he was still brilliant, he never downed tools".
Final whistle at Anfield.
And former Liverpool FC star Carragher was quick to label the comeback as the greatest ever European night at Anfield.
He added: "He started playing well because he wanted to leave".
The midfielder replaced the injured Andy Robertson at half-time and scored twice, with Origi scoring the victor.
Rolling around on the floor, waving imaginary cards and generally antagonising the opposition is what Suarez likes to do pretty much every time he steps out on any pitch.
While at normal speed it appeared the collision was nothing more than an accident, with Robertson running into Suarez mid-stride, replays showed hints of a kick-out from the Barcelona man. "It's absolutely incredible", Liverpool-born Fowler told BT Sport. Robertson obviously goes down, I don't know if he's got a dead leg because of that.
Messi and Ronaldo also saw their streak of being the only two players to win the Ballon d'Or for a 10-year period ended when Luka Modric claimed the 2018 award.
"But he is that type of player".