Blues took a first half lead through Chris Wood at the KC Stadium but were beaten 2-1 on the night by Nick Barmby's side.
"We're on the back of four tough away games now, having gone to Blackpool, Braga, Cardiff and Hull. That's a tough period in any season," the Blues boss said after the match.
"Over 90 minutes we certainly had enough chances not to lose the game.
"After going in 1-0 up at half-time, what you can't afford to do is concede as early as we did in that second half.
"We got back into the game after that but we're victims of not being clinical enough with the good chances we had and not defending well enough over 90 minutes.
"It's frustrating because, if you look at the chances we've created, we shouldn't have lost the game.
"But one thing about a difficult time is you've always got the opportunity to put things right and go on another good run."