Jim Mallinder admitted Saints rode their luck at times as they progressed to the LV= Cup final at the expense of Saracens.
A second-half hat-trick from George Pisi secured a 26-7 win to set up a shot at silverware against either Bath or Exeter at Sandy Park next Sunday.
But Saints did it the hard way, having gone in at half-time behind as Saracens dominated the first period.
A try from full-back Ben Ransom allied with Ben Spencer’s conversion put the away side 7-6 up before centre Marcelo Bosch had a try disallowed.
And Mallinder admits his men were lucky not to have been further behind at the break, hailing their ability to fight back in the second period to earn the win.
“They had the try (that was disallowed for a forward pass) and came close on another couple of occasions,” said the Northampton director of rugby. “We rode our luck in that first half.
“At half-time, we were under the cosh a little bit, we admitted that, but we’re really pleased with the way we came through to win.”
Mallinder felt the loss of centre Tom Stephenson was a factor in his side’s difficulties during the latter part of the first half.
Stephenson was forced off with a knee injury after just 12 minutes, with Stephen Myler entering the fray and Will Hooley moving to centre.
And Mallinder said: “We were a little bit rocked by losing Tom Stephenson. It’s never easy when you lose a player early and Tom’s been our defensive captain in the past few weeks.
“Having to make that change, with Will Hooley going to inside centre, disrupted us a little bit and gave Saracens the opportunity to get on the front foot
“But we regrouped in the second half and defensively we were much stronger.”
On Stephenson’s injury, Mallinder added: “He’s sprained his knee so hopefully it’s not too bad. FIngers crossed he’ll be fit and available for next week.”