Bruce Reihana’s try and five penalties from Stephen Myler enabled Northampton to continue their unbeaten home run which stretches back to March 2007.
Reihana was sent in for the crucial score by Ben Foden, the player whose impressive form had kept the captain on the bench in recent Guinness Premiership matches.
Foden, left out of the England 22 to face Wales after making his debut as a replacement against Italy, came into the line to release his skipper – recalled on the left wing with Sean Lamont away on Scotland duty – for a short dash to the line in the final minute of the first half.
After surviving a shaky opening period, in which they fell 9-3 behind, Northampton rallied to take control against a Saracens side playing their first match since the announcement that director of rugby Eddie Jones will be replaced by South African Brendan Venter at the end of the season.
Saracens, led by former All Blacks scrum-half Justin Marshall, provided the early threat with Glen Jackson, Alex Goode and Noah Cato linking up dangerously to cut through the home defence before they were stopped just short.
Veteran Marshall, making his Guinness Premiership debut for Sarries after being recruited as cover for the injured Neil de Kock and Moses Rauluni, was a constant threat with his probing runs. The pressure paid off as Saints conceded penalties in front of their own posts and Jackson kicked the visitors ahead in the fourth, ninth and 20th minutes, with Myler’s 15th-minute penalty opening Northampton’s scoring.
Saints’ 20-year-old hooker Brett Sharman, a recent arrival from South Africa’s Blue Bulls, was denied a debut try when referee Greg Garner, handling his first Premiership match, ruled that Marshall’s kick had rebounded off him.
Saracens, who dominated the first half, then had a try ruled out in the 31st minute. They stretched the Northampton defence to breaking point to leave Goode a clear run for the line but referee Garner penalised them for obstructing the home defence by crossing earlier in the move.
Saracens really should have had more to show for their first-half supremacy but handling errors spoilt some promising moves.
Then, against the run of play, Northampton hit back with their opening try in the 39th minute. Centre Jon Clarke and flanker Mark Easter did the hard work before Foden sent Reihana over in the left-hand corner.
Myler’s second penalty three minutes into the second half put Northampton ahead for the first time in the match. The fly-half missed the opportunity to increase his side’s lead when his long-range penalty fell short after skipper Andy Farrell had been penalised for not releasing the ball after being isolated and caught in possession.
The balance had swung with Northampton dominating after the interval as the centre partnership of Clarke and James Downey and the mobile back row of Mark Easter, Neil Best and Roger Wilson drove powerfully into the heart of the Saracens defence.
With Saracens now falling foul of the referee, Myler landed three more second-half penalties with Jackson replying with his fourth kick and a last-minute drop goal which salvaged a losing bonus point.