Walker, whose below-par performances have been criticised by some Citizens supporters this term, started as captain and played the full 90 minutes of Man City's 2-0 Champions League defeat to Juventus on Wednesday night.
Defeat in Turin represented the Citizens' seventh in their last 10 games across all competitions and they are now in danger of failing to qualify for the knockout rounds of the Champions League, sitting just one point above the elimination zone with only two games remaining.
After the match, Walker released a statement confirming that he was the subject of "vile" racist abuse on Instagram and has called for tough action to tackle online abuse.
In a statement from Man City, the club "strongly condemns" the racist abuse that Walker was subject to online and will offer the 34-year-old their full support "following the disgusting treatment he has received."
Walker is expected to feature for Man City in Sunday's Premier League Manchester derby against rivals Manchester United at the Etihad Stadium, and ahead of the contest, Guardiola has offered his support to the defender.
Guardiola: "We are in full support of Walker"
"First, it's unacceptable, but not because it's Kyle, for every human being," Guardiola said at a press conference on Friday. "Unfortunately, today in the real world it happens many times.
"Of course, it's not necessary to even say but from all the staff, backroom staff, all the people, he has the support of the entire club.
"It's not because it's Kyle. Unfortunately it happens in every department of our society. It's completely unacceptable, but we are in full support of him."
Guardiola added that he has not spoken directly to Walker since the racist abuse was directed towards him after the defeat to Juventus.
Meanwhile, Kick It Out, an organisation that works to combat discrimination in football, have said that Walker had been the subject of "disgraceful abuse" which "again highlights the deep-rooted issue of online hate".
A statement, as quoted by Sky Sports News, read: "With reports of online discrimination to Kick It Out more than doubling last season and platforms failing to act decisively, we stand firmly behind Kyle's call for social media companies and authorities to do more."
Walker has made 315 appearances for Man City in all competitions since joining the club in 2017, and the England international has won 17 trophies, including six Premier League titles.
Written by
Oliver Thomas