Saints director of rugby Chris Boyd felt his team 'ran out of juice' as they were thumped 42-12 by Exeter Chiefs in the Gallagher Premiership semi-finals at Sandy Park.
At half-time, Saints were right in the hunt as they only trailed 14-12, and really should have been in front.
Cobus Reinach missed a gilt-edged chance to run in a try under the posts just before the break, dropping the ball, and it proved to be a costly error.
Exeter were rampant and ran in four unanswered tries in the second half to secure an emphatic victory and end the Saints' title hopes.
Boyd's men had also been under the cosh in the first half as they started badly and trailed 14-0, and he felt the effort his players put into getting back into the game before the break took its toll.
"I am not sure they were 30 points better than us, but at the end of the day they were better than us," said the Saints boss.
"We didn't have an answer in the last 30 minutes as they strangled us out.
"That was probably as a result of the first 20 minutes when we had to do so much work, that we just ran out of juice probably."
It was the second successive Saturday Saints had been on the receiving end of a heavy defeat in Devon, and Boyd felt the semi-final followed a similar pattern to the last-day Premiership loss.
"It's the same as the previous week," he said. "We are playing against a side and the way they play we have to be really accurate, and really disciplined.
"We fell off our game a couple of times, and gave them some opportunities.
"After half-time they got two quick tries and then just put the planks on, and we weren;'t able to control the game."