Mark Robins' side have been beaten 2-0 by Morecambe at the Globe Arena.
Vadaine Oliver gave Morecambe the lead before Callum Lang's second half striker sealed victory for the home side after a dissapointing display from the Sky Blues.
"That was men against boys from start to finish," said Robins.
"It is very difficult to come to terms with just now. The players certainly know how I feel.
"That showing today was nowhere near a side who deserve to be anywhere near the top end of the league.
"No real know-how and no real fight. There were some youngsters in there but that is no excuse. We looked lacklustre.
"You have got to work hard and match the opposition and we did no do that today. Vadaine Oliver has just had the best game of his life and he really put us under pressure at the back.
"We were disjointed and never worked them out really."
Duckens Nazon was substituted at half-time and replaced by Devon Kelly-Evans, and the Sky Blues did battle back into the game temporarily before Lang's second half strike put the game beyong City.
"Nazon was not giving us anything and something had to change.
"I tried to start with the three of them all on [Nazon, McNulty and Biamou], but if it does not work then we have to try and do something to stop their attacks because they were putting us under pressure. They found it too easy against us.
"The first thing that they have to do is fight and they did not fight at all today. We were way off them from the start. We looked short of any confidence.
He added: "It is embarrassing. We have had supporters travel. The weather is horrenduos and they have had to work hard to get up here and we have not given them anything.
"It really annoys me and it hurts. People pay good money and we have not get anywhere near them."