Saracens had the better of the early exchanges and raced into an 18-point lead following tries from David Strettle, Kelly Brown and Marcelo Bosch.
But Saints fought back and set up a grandstand finale when Luther Burrell and Lions international George North crashed over the whitewash to close the gap to just four points.
The win over second-placed Saints means that Sarries need just two more points to claim top-spot and take a home semi-final into the play-offs.
And with a European Cup semi-final against Clermont Auvergne on the horizon as well, Sarries director of rugby Mark McCall is hoping to get Farrell back as quickly as possible.
"It's too early to say about Owen. It's a foot injury and you never know with foot injuries," he said.
"Owen doesn't remember when it happened. We'll have news later in the week. He couldn't kick with it.
"It was tight at the end but I wouldn't want to ignore the first 70 minutes. We were really good and hard to handle at times."