Birmingham City lost 2-0 to Huddersfield Town yesterday afternoon.
Birmingham were punished for being slow out of the blocks when Huddersfield score in the first minute through Joe Lolley.
It proved to be a deficit that the Blues were unable to overcome, with the side eventually falling to a disappointing 2-0 defeat.
And Rowett said: "Incredibly disappointing start and I think when you start that badly so early on, maybe one or two of the players were a little bit shell-shocked, the fans were definitely shell-shocked and it was disappointing.
"From there on in, I felt we got in some okay positions.
"Once again, before they scored the second, we've had three very good chances and at the moment we're just not ruthless enough at home."
Birmingham were outplayed for large portions of their match against Huddersfield, with the away side looking sharp throughout the contest.
David Wagner’s impact on the Terriers’ team was clear, but Birmingham’s performance was below their usual standard.
The Blues have been a very solid outfit under Rowett so far, but with injury problems mounting they have struggled over recent weeks.
Birmingham have now failed to win any of their last three matches and they will be eager to get back to winning ways, to ensure that they stay in touch with the play-off chasing pack.
At the moment Rowett’s men are in eighth place in the Championship table, with their next fixture coming against high-flying Middlesbrough.