With his team leading 5-0 after 18 minutes and threatening Premier League scoring records, Manchester City manager Pep Guardiola sat with his arms folded in his dugout and might even have looked a little guilty.
Everton had a supposedly benign run of fixtures to start the season but have only come away with seven points from six games, with City visiting next week.
"It's probably a bit of shock, embarrassment", Foster said to Sky Sports.
"They were scary at times. In all honesty, it could have been double digits".
Three more goals in the second half gave City their biggest ever top-flight win as they closed the gap to leaders Liverpool to two points, although Jurgen Klopp's side do have a game in hand.
Watford continued to struggle to contain their opponents, but City began to misfire in front of goal.
Still smarting from the critical reaction to City's 3-2 defeat at Carrow Road, Guardiola accused some former players of lacking respect for a team who have won the title for the past two seasons.
"We are just doing our job", said Fernandinho, who was untested in a defensive role forced on him by injuries to team-mates.
"We were ruthless in terms of five shots, five goals". "But we did the opposite, and we were more aggressive and made a very good second half". The relaxation you play with, the tension they play with, so it's hard to say.
It was a day to remember for Manchester City supporters, as their side bounced back from a disappointing defeat at Norwich to put on a stunning show against Watford on Saturday afternoon.
"It is hard to know if he will be OK or not", Flores said.
After playing a part in so numerous goals, it was fitting that De Bruyne should score the eighth, and the best goal of the game, with a powerful shot from just inside the penalty area. Sometimes we play so good and make a very good performance but don't score any goals, now we've scored a lot of goals.
"Bernardo was the best player last season", he added.