Saints were struck by yellow peril as they suffered an 18-15 defeat against Sale Sharks at the AJ Bell Stadium on Saturday evening.
Jim Mallinder's men were hit by three sin-binnings, with Michael Paterson, Jamal Ford-Robinson and Ben Foden all forced to sit out 10 minutes of the match.
And it was to cost Saints dear as they conceded two tries while down to 14 men and it undid the early good work that had seen the away side earn a 12-3 lead.
Tries from Cobus Reinach and Mike Haywood had put Saints in control before Sale fought back, forcing Paterson and Ford-Robinson to infringe.
The Sharks were 12-10 down at the break, but took the lead early in the second period before Saints levelled the scores.
And then came a controversial moment as Foden was sin-binned for what referee Karl Dickson viewed as a deliberate knock-on, with the decision appearing slightly harsh.
Will Cliff landed a penalty soon after to put Sale 18-15 up with 17 minutes remaining and that was how it stayed as Saints suffered their fourth successive Aviva Premiership defeat.
Mallinder's men applied some pressure from the kick-off, but Sale went ahead as their first venture into the opposition half resulted in a penalty for offside, which Faf De Klerk kicked.
But that did not deter Saints and after Reinach worked hard to close James O'Connor's attempted clearance down, the ball bounced kindly for the South African scrum-half to
gather and score.
Harry Mallinder's conversion attempt was scuffed, leaving the score at 5-3, but Saints soon extended their lead.
Tom Wood made a rapid break, forcing Sale to scramble and after the home side conceded a penalty, the ball was kicked to the corner.
Saints worked it well and Haywood eventually managed to get the ball down next to the right post, with Mallinder adding the extras to make it 12-3.
But former Sale lock Paterson was soon heading for the sin bin as he tackled De Klerk from a quick tap penalty, having failed to retreat.
Sale strangely turned down a simple kick at goal and booted the ball out behind rather than in front of the field position they occupied.
That gave Saints the chance to hold out as they defended close to the edge of their own 22, and the Sharks knocked on, wasting a good chance to grab some points.
But another yellow card, this time for prop Ford-Robinson, gave them even more of an opportunity after pressure was applied in the maul.
It was penalty after penalty as Sale cranked up the heat in the freezing conditions, but Saints held Sale up just before Paterson returned.
Eventually the home team's pressure did pay as De Klerk picked the ball up from a scrum five metres out and cruised through a sizeable gap to score.
De Klerk added the extras to cut the gap to two points at half-time and Sale scored again just before Saints were restored to 15 men as flanker Ben Curry raced in out wide.
The conversion was missed, but the Sharks now held a three-point advantage and Saints had to respond.
Sale thought they had scored again soon after as Marland Yarde spotted a gap and dotted down, but there was clear obstruction in the build-up and Saints were awarded a penalty.
Saints were desperate for a spell of possession and when they finally got it, they won a penalty, which Mallinder landed with aplomb.
The game continued in nip and tuck fashion until Saints were struck with another sin-binning.
Foden was yellow carded for what was viewed as a deliberate knock-on, though the decision looked harsh as the ball looked to have struck him while he was trying to wrap to make a tackle.
Replacement Cliff landed a penalty to put Sale back in front with 17 minutes to go and the game was heading for an enthralling conclusion.
Saints turned down a decent shot at goal with three minutes to go, but their decision to kick for touch wasn't rewarded as the ball slipped from their grasp inside the Sale 22.
The away side were to get one final chance as they again opted to go for the corner, but Sale stood tall, forcing the turnover and celebrating the victory.
Sale Sharks: Haley; Solomona, James, Jennings (Van Rensburg 51), Yarde; O'Connor, De Klerk (Cliff 55); Harrison, Webber, John (Aulika 61); Evans (Nott 69), Ostrikov; Ross (c) (Neild 28), B Curry, Strauss.
Saints: Mallinder; Estelles, Hutchinson, Stephenson, Foden; Grayson (Myler 75), Reinach (Groom 64); Waller, Haywood, Ford-Robinson (Hill 66); Paterson, Dickinson (c); Wood, Gibson, Harrison (Eadie 72).
Referee: Karl Dickson