After the final whistle, Manchester City earned a crucial three points toward earning a spot into the knockout stage of the UEFA Champions League.
"But football is like this, like when Fernandinho slipped and Messi scored in Barcelona".
With Barca enjoying an increasingly healthy share of possession as the half progressed, a loose Sergi Roberto pass eventually found its way to Sterling, whose ball across the face of goal teed up Gundogan for a simple finish.
But the 45-year-old Spaniard said that when it was "11 v 11" in the first game, his side performed much better than for the 38 minutes on Tuesday night.
Pep Guardiola hailed a historic victory after Manchester City came from behind to stun Barcelona on a memorable Champions League night at the Etihad Stadium.
Andre Gomes hit the bar for Barca as they attempted to draw level, but the La Liga side were undone when Gundogan grabbed his second late on to secure Man City the victory.
The speedster had another awesome performance for the citizens like the ones he had during the start of the season, he even recorded an assist and was a huge factor in Guardiola's side win.
"City took advantage of our errors".
However, with just 20 minutes on the clock, Lionel Messi and Neymar combined on a textbook counter attack to put Luis Enrique's side into the lead, and it looked as though it may well be the same story all over again for Pep Guardiola and his Manchester City side.
Guardiola may have shared fans' pain when Sterling was brought down in the area for a penalty early on only to be booked for diving. And Barcelona did beat City 4-0 two weeks ago at home.
That sparked life into the entire team, who looked to have a renewed sense of belief that Barcelona were vulnerable under pressure, even if they were still risky in attack.
How far can City go?
The inevitable Lionel Messi put the visitors in front at the end of a stunning breakaway with his 90th Champions League goal.
City will feel that after beating Barcelona in this manner they can be a match for anyone, although questions remain about a defence that is not exactly risk-averse. Yet these were just a couple of many memorable moments that contributed to what will be remembered as a classic, and what was perhaps the dawn of a new era for City in Europe. There can be no bigger tribute than that.
Ilkay Gundogan netted a brace and Kevin De Bruyne scored from a wonderful free-kick to guide the Cityzens to glory.
"Of course now they realise, 'Wow, we (beat) the best team, ' so we are able to do that".
City produced the goods when humiliation beckoned again with Barca offering what coach Luis Enrique called "one of the best 40 minutes we have played on a stage like this against top-quality rivals".
City's handsome 3-1 victory on Tuesday, carrying the slick pass-and-move imprints of the best Guardiola creations, felt like a landmark for the wealthy "wannabes" who have long strived for the continental performances to match their financial clout. When you play so well for the first 40 minutes, if after things don't go to plan, it's a odd feeling. I think the club gives us time. "Now they will realize, 'Wow, we won against the best team, '" said Guardiola.
The footage, despite referencing the Champions League, was actually captured during City's Premier League clash with West Brom on Saturday.