Alex Iwobi and Everton gave the champions a decent fight at the Goodison Park but ultimately succumbed to a 3-1 defeat thanks to goals from Gabriel Jesus, Riyad Mahrez and Raheem Sterling.
The result left Everton boss Marco Silva disappointed although he was pleased with his players' performances, bar one, in making Pep Guardiola's men work hard for the three points.
Alex Iwobi started on the bench but had to be introduced for Walcott after just four minutes following the English man's head injury. The Nigeria international took some time to settle in as Manchester City bossed the opening half hour.
However, once the Citizens took the lead through Brazil's Jesus, the Toffees shifted into top gear, troubling the away team until their equalizer arrived following good work from the Super Eagles playmaker.
Two sloppy goals were later conceded in the second half to undo the fine work Silva's men had done all afternoon, leaving the manager disappointed.
“The first 20 minutes our performance wasn't good enough but after their goal we responded strong. We had some good moments. We were faster and quicker and made problems for them and equalised,” Marco Silva told BBC Sports as monitored by Soccernet.ng.
“We created problems for them and had a good moment with Gylfi Sigurdsson. They had a bit more possession, which is normal against most teams.
“But we had a good attitude from our players and, to be honest, we had the best chances before they scored to make it 2-1, through Mina and Calvert-Lewin. There was a big save by Ederson.
“It was a good game, a competitive game. We didn't get the points but there were lots of positives.
Everton's goalkeeper Jordan Pickford was at fault for City's second goal as the England international allowed Mahrez's free-kick to steal past him, leaving both manager and keeper frustrated.
“It's normal for the keeper to be frustrated when he concedes a goal on his side but now we'll analyse it with him, like always,” Marco Silva added.
