"We've had a very difficult spell and there were signs of tiredness," the Rovers boss said after the 1-0 defeat at Ewood Park.
"It was disappointing to concede a goal just before half-time and you can't afford to lose your concentration for a second against top quality players.
"It's disappointing to lose, especially after we went into the game with confidence high, but we can't complain about the players and the work they've put in over a long period.
"It's the first time the sun has shone in Blackburn for some time and I think that sapped our energy, but we'll bounce back.
"Whoever won today was going to say they would have an advantage for the semi-final but how much of an advantage is debatable."