The England full back came on as a late substitute and was deployed in goal after Claudio Bravo - who himself had come on as a half time substitute for Ederson – was sent off.
And in his post-match press conference, Guardiola was full of praise for Walker’s willingness to help the team's cause.
“Xabier Mancisidor, our goalkeeping coach, suggested Kyle for his courage, and we were lucky to only concede one shot,” said the City manager.
"Congratulations for the courage and desire to help the team.
“Everyone knows how difficult it is to play Atalanta so the fact that we have taken four points off them is a big success for us particularly with the injuries and difficulties.
“We played well in the first half and then dug deep in the second.
Play the video to watch Pep's press conference in full...