Mark Robins felt it was “a game too far” for his side after the Sky Blues suffered defeat to Sheffield Wednesday at Hillsborough on Saturday.
City were beaten by a second-half goal from Tom Lees bringing an end to their eight-game unbeaten run in the league.
The manager was disappointed with the result, but believes it was a case of one game too many, playing their ninth fixture in just 30 days.
Robins said: “I’m disappointed with the result, it was a really difficult game, I’m not going to make any excuses, it was a horrific pitch, but we weren’t ruthless enough in front of goal.
“We created decent opportunities, they cleared one off the line, we had the ball in decent areas and didn’t make the most of it, it was tough.
“We gave them a soft free-kick and they’ve scored from it, that’s been something that we’ve been really good at.
“We just feel it was a game too far for us, after the amount of games we’ve had, it was the ninth game in the run, you could see that, they’ve had an extra day’s rest as well on top of that.
“It was a difficult game and a difficult result, no one should hang their heads they’ve done fantastically well and they’ve given me everything they had.
“We need to move on from it really quickly, we’ve got some tough games coming up, but they need a bit of a rest before those games.”
Robins also felt his side were the better team in South Yorkshire, but struggled to get a foothold in the game due to the tricky playing surface.
“Energy wise we looked alright, the pitch dictated a lot of it, everyone was slipping all over the place you couldn’t really get any momentum or a foothold in the game.
“They’re fighting and they’ve not won since Tony Pulis came in, that’s the biggest disappointment for us we wanted to try and keep our run going, this league is very, very tough.
“The results can turn just on that, I thought we were the better team, we showed a lot of intent to try and go and score a goal, it was very difficult to get any control because of the pitch, losing Tyler Walker didn’t help, that was a blow.”