Premiership leaders Northampton conceded just their second defeat of the season on Saturday, going down 19-6 to Sale Sharks at AJ Bell Stadium.
Mark Cueto, Marc Jones and Tom Brady all scored tries in a terrific first half from the Sharks, as they climb further towards the top four.
Saints' returning Six Nations stars looked sluggish, and despite pressure in the second half looked unlikely to mount a comeback.
Saints took an early lead through the boot of Will Hooley, but were dealt a shock when Cueto scored the first try of the match.
Dwayne Peel ran 30 metres, and when the ball was eventually worked wide, Cueto crept over in the corner. Danny Cipriani converted from a tight angle, but Hooley was on hand with another penalty to keep the scores close.
Northampton were reeling just before the break, as Sale scored their second. Jones scrambled across the line after a mountain of Sharks pressure.
A resulting brawl led to Dylan Hartley and Sammy Tuitupou going to the bin.
There was still time for the visitors to fall further behind, with Brady benefiting from a super kick in behind from Cipriani to give Sale a shock 19-6 half time lead.
Saints came out of the blocks quickly, but were unable to cross thanks in part to some excellent last ditch defence from the home side.
A stubborn Sharks defence kept the second half scoreless, as Jim Mallinder's men plugged away looking for any sort of points.
Despite their continued efforts, Steve Diamond's men held on for one of their biggest victories in recent memory.
Tom Brady's performance will have stood out, as he managed to tame the not inconsiderable talents of George North on the wing and get himself on the scoresheet.
Tries: Cueto, Jones, Brady
Cons: Cipriani 2
Yellow card: Tuitupou
Pens: Hooley 2
Yellow card: Hartley
Sale Sharks: 15 Tom Arscott, 14 Tom Brady, 13 Jonny Leota, 12 Sammy Tuitupou, 11 Mark Cueto, 10 Danny Cipriani, 9 Dwayne Peel, 8 James Gaskell 7 David Seymour, 6 Dan Braid, 5 Michael Paterson, 4 Jonathan Mills, 3 Vadim Cobilas, 2 Marc Jones, 1 Eifion Lewis-Roberts.
Replacements: 16 Aston Croall, 17 Ross Harrison, 18 Henry Thomas, 19 Andrei Ostrikov, 20 Mark Easter, 21 Will Cliff, 22 Nick Macleod, 23 Rob Miller
Northampton: 15 Ben Foden, 14 Jamie Elliott, 13 James Wilson, 12 Luther Burrell, 11 George North, 10 Stephen Myler, 9 Lee Dickson, 8 GJ van Velze, 7 Tom Wood, 6 Calum Clark, 5 Christian Day, 4 Courtney Lawes, 3 Salesi Ma'afu, 2 Dylan Hartley (c), 1 Alex Waller.
Replacements: 16 Mike Haywood, 17 Gareth Denman, 18 Tom Mercey, 19 James Craig, 20 Phil Dowson, 21 Kahn Fotuali'i, 22 Will Hooley, 23 George Pisi.
Venue: AJ Bell Stadium
Referee: Luke Pearce
Assistant Referees: Paul Burton, Kelvin Stewart
TMO: Keith Lewis