Pep Guardiola believes Walker deserves the three-game ban.
The UEFA handed Walker a three-match for kicking RB Leipzig’s Andre Silva back in December.
He will miss the last-16 second-leg tie this Wednesday against Sporting.
Pep Guardiola was not happy with the defender’s actions and he did not agree when City was trying to reduce the three-game ban.
“He deserved the three-game ban. When a player does a stupid thing, he deserves to be banned for three games. I’m not so kind to Kyle in this kind of action. I’m still so angry with him,” the City manager said.
“It’s not necessary to discuss with him, he knows it. Kyle is so important for us, you saw the game he played against United? But in Leipzig when we had already qualified, 80 minutes in and he made this kind of action?
“He deserves the three games. The club appealed but I did not agree. They have to do it because in other similar cases it was just two games [but] he deserved it. Hopefully he learns for the future.”