Northampton director of rugby Jim Mallinder blamed fatigue for his side's dramatic defeat by Leinster in the final of the Heineken Cup on Saturday.
A week earlier Northampton had been involved in a bruising Premiership semi-final loss at Leicester.
Leinster in contrast were able to rest key players during their comfortable Magners League semi win over Ulster.
"We were tired, you could tell at half-time," said Mallinder after their 33-22 defeat in Cardiff.
Leinster fought back from 22-6 down at the break to score 27 unanswered points to seal a stunning victory.
"It was just a case of telling the lads to dig in for just 40 more minutes but the long season took its toll in the end.
"It was a full-on game, it was very fast and credit to all the players involved."
Mallinder withdrew the likes of Soane Tonga'uhia and captain Dylan Hartley as his side trailed in the final quarter.
The Saints boss admitted the 11-3 defeat to Leicester a few days earlier had taken its toll on several of his star players.
"It was because they were exhausted," admitted Mallinder.
"They were shot. It would have been nice not to have had a full-on game last week, and Leinster managed to take their five best players off in their game. We could not do that against Leicester.
"But we will come back stronger. We have always improved and we have said, in the huddle at the end, let's see if we can win it next time."
Northampton full back Ben Foden said the feeling of dejection on the final whistle was "150% the worst I have felt after a game".
The England star added: "It is a bitter pill to swallow. We play this game to be in moments like this.
"This is the pinnacle of professional rugby at club level, to get to our Champions League final and going in at half-time 22-6 up, we had one foot through the door.
"But no final is won in 40 minutes. They blew us away in that 15 minutes after half-time. They were crowned European champions for a reason, they played tremendously well all season.
"For a neutral it would have been a tremendous spectacle to watch, a hell of a final, but when you are on the wrong end of the result it always stings no matter how you have lost.
"We are a young team and these moments bring us together."