Malky Mackay felt Cardiff City created enough chances after a 2-0 home defeat by West Ham United in the first leg of the Championship play-off semi-final.
A first-half double from Wales international Jack Collison put the Hammers in command and in a strong position to face either Birmingham City or Blackpool at Wembley later this month.
However, Cardiff came close to scoring before Collison's ninth minute opener and had further opportunities in the second half.
Mackay was left to rue poor defending for the first goal and the Bluebirds now head to Upton Park on Monday with a mountain to climb to progress.
When asked the reasons why Cardiff are behind in the tie, Mackay told Sky Sports: "Goals, it's as simple as that.
"The first one is certainly poor defending from us at three points during the move. The second one is complete random luck as the ball takes a huge deflection.
"We had three or four real good chances tonight that went the other side of the post.
"We had a real good one in terms of Peter Whittingham's, Kenny Miller has shaved the post.
"In the second half we came back into it again and had two or three great chances. We had one cleared off the line, Kenny Miller was just wide of the post, Mark Hudson was just wide of the post."