Northampton Saints handed Saracens only their second defeat of the season in the LV= Cup on Saturday, with a 19-3 victory.
Wingers Chris Ashton and Bruce Reihana went over for tries either side of the break and Stephen Myler kicked the rest of the points for Saints, who have now won two from two in Pool Four.
Guinness Premiership leaders Sarries, whose only other defeat this term came in Europe at the hands of Jonny Wilkinson's Toulon, had a largely second-string team out and it showed as they were bullied in most departments.
Fly-half Alex Goode landed their only points with a first-half penalty, but their cup hopes are still alive owing to their win against Bath last weekend.
The match began under grey skies before driving rain and fierce winds arrived 15 minutes in.
Such conditions played havoc with both teams' kicking games, with Myler off target with a relatively straightforward penalty attempt after seven minutes.
Goode, who has been playing at full-back this season even though he prefers the number 10 spot, judged the wind perfectly to land his first penalty and put Sarries 3-0 up in the 20th minute.
But Saints hit back immediately with a try created by a moment of brilliance by Ben Foden, who cut a sensational line when returning a deep punt forward by the visitors.
Having breezed through three sprawling tackles, the full-back, not needed by England this weekend, then kicked on for Ashton to ground in the right corner.
Myler could not convert that try and also skewed wide another easy penalty three minutes before half-time.
The England Saxon did, however, knock over a tough goal from the right touchline in stoppage time, after Saracens substitute prop Tom Mercey was sin-binned for hands in the ruck, to put Saints 8-3 ahead at the break.
Down to 14 men, the home side applied the pressure at the start of the second half and their powerful scrum forced a penalty three minutes in that Myler converted.
Goode was short and wide with a long-range penalty but playing with the wind now and back to their full complement, Saracens began to gain more of a foothold in the match.
That did not stop them falling further behind in the 55th minute when Reihana bulldozed his way over from range, moments after making an original break that caused panic in Sarries' ranks. Myler failed to add the extras but Saints were 16-3 ahead and cruising.
With their scrum being bullied and their line-out malfunctioning, Saracens had no platform to fight back and Northampton came close to adding a third try on a couple of occasions, only to be denied by last-gasp defending by the visitors.
Myler took his haul for the afternoon to nine points with a penalty, his third of the game, in the 76th minute, and try as they might, Saracens' inexperienced side could not score a consolation try despite sustained late pressure.
Northampton Saints: 15 Ben Foden, 14 Chris Ashton, 13 Jon Clarke, 12 James Downey, 11 Bruce Reihana, 10 Stephen Myler, 9 Lee Dickson, 8 Roger Wilson, 7 Scott Gray, 6 Phil Dowson (capt), 5 Juandre Kruger, 4 Christian Day, 3 Santiago Bonorino, 2 Brett Sharman, 1 Soane Tonga'uiha.
Replacements: 16 Joe Gray, 17 Jon Vickers, 18 Alex Waller, 19 James Cannon, 20 Mark Hopley, 21 Alan Dickens, 22 Barry Everitt, 23 Joe Ansbro.
Saracens: 15 Richard Haughton, 14 Noah Cato, 13 Rodd Penney, 12 Kevin Sorrell, 11 James Short, 10 Alex Goode, 9 Kevin Barrett, 8 Jackson Wray, 7 Andy Saull, 6 Don Barrell, 5 Mouritz Botha, 4 George Kruis, 3 Carlos Nieto, 2 Ethienne Reynecke (c), 1 Kasiano Lealamanua.
Replacements: 16 Jamie George, 17 Rhys Gill, 18 Tom Mercey, 19 Hugh Vyvyan, 20 Justin Melck, 21 Neil de Kock, 22 Owen Farrell, 23 Kameli Ratuvou.
Referee: Gwyn Morris