The 1-0 loss in Porto extended Guardiola’s wait for Europe’s biggest prize, now stretching back to his 2011 triumph with Barcelona.
The Spaniard was questioned for a number of tactical decisions, none more so than his omission of Fernandinho.
But Walker has claimed the flack his boss receives is unfair and instead admitted that his side should have created more than the one shot on target they actually registered.
“Listen, people can talk. I’ve seen a few things or my mates have text me about tactics, personnel, this, that and the other,” Walker told Mail Sport.
“It’s a game of football, it’s 95 minutes and anything can happen. Obviously, we wanted the result to go our way but the manager, or whoever, picks who he feels can go and get the result and what’s best for the club.
“When he gets it right nobody says anything and when he gets it wrong – or when they think he’s got it wrong – people are questioning things.”
The England international continued: “I think it’s a little bit unfair sometimes when as soon as Manchester City don’t win then it’s tactics or maybe players on the pitch, but we needed to do more and it’s as simple as that.
“I don’t think we created enough in the game and I don’t think I’m speaking out of turn by saying that, I think everyone could tell on the pitch.”
City’s defeat in Portugal also prolongs their wait for a Champions League, failing to conquer Europe despite spending more than £750m on arrivals since Guardiola’s appointment in 2016.
On City’s latest failure in Europe, Walker accepted that without a winners’ medal from that competition, this current team can’t be ranked alongside some of the best in history.
“I think with the squad we’ve got, with the manager we’ve got, with the club that we’re playing for, we should be going and winning the Champions League, we all know that,” he explained.
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“We all know that the players, at least since I’ve been there, have been signed to go and get it.”
“Yeah, okay, we can go and win the Premier League and I think we’re so fortunate to win three in four years, but we do need a Champions League as a club because I hear a lot of people saying it’s probably one of the greatest Premier League teams ever.
“Okay, yeah, that’s great, fantastic for me to even be involved in a team like that, but to be classed as one of the best teams ever I think you need the Champions League and that’s something that we are missing.”