Saints ended their three-match league losing streak as a moment of magic from Ryan Lamb helped see off spirited London Welsh.
Lamb’s superb crossfield kick was collected by Ken Pisi late in the first half to give Saints the platform for victory.
But Welsh more than held their own and were 10-3 up early on as a penalty try and the boot of Gordon Ross, who finished with 11 points to his name, did the damage.
Gerrit-Jan van Velze’s yellow card in the afterrmath of the try threatened to cost Saints, but Welsh too fell victims to yellow peril as Franck Montanella and Dan Caprice were also binned during a feisty first half.
Saints made the most of their spells with the extra man, replying with a penalty try of their own and Pisi’s score allied with 13 points from the boot of Lamb clinched a 23-16 win.
The much-maligned No.10 also ended up with the man of the match award, which attracted some jeers when it was announced.
But there could be no doubt that his superb piece of skill for Pisi’s score was the game’s pivotal event and one which keeps Saints in touch at the top of the table.
Northampton boss Mallinder, who this week confirmed the departure of Paul Grayson from his coaching team, brought back the big guns in a bid to put the Premiership losing streak to bed.
Courtney Lawes, Soane Tonga’uiha and Brian Mujati all returned to the side, with Martin Roberts also in, for the injured Lee Dickson.
But London Welsh weren’t fazed by the Saints pack and it was the away side who turned on the power early on the get the game’s first try.
They put together an unstoppable driving maul, flying towards the Saints line and earning a penalty try from referee David Rose.
Saints No.8 van Velze was sin-binned in the process and as Ross slotted the conversion the Premiership surprise package were 7-0 up inside the first 10 minutes.
Lamb brought Northampton back to within four moments later, landing a drop goal but Ross replied instantly as Welsh grabbed a penalty.
The visiting fly-half had a chance to extend his side’s lead to 10 points soon after but this time fluffed his lines as Saints breathed again.
Van Velze returned and the home faithful started to find their voices as Welsh got a dose of their own medicine, finding themselves crushed under a Saints stampede.
The driving maul resulted in a penalty to Mallinder’s men and Welsh prop Franck Montanella was sent to the bin.
Saints opted for the scrum and Rose continually awarded them penalties to the frustration of the fans, who were demanding a penalty try.
And it eventually came, giving Lamb the chance to haul his side level with 14 minutes of the half to go.
Montanella returned from the bin to boost the Welsh numbers but no sooner had the forward got back on the pitch than the away side lost another player to a yellow.
This time Caprice was in the dock as he put in a high tackle on Jamie Elliott and Saints again made Welsh pay, scoring a superb try that saw Lamb send a superb cross-field kick into the path of Pisi, who picked up to score.
It was a moment of magic from Lamb, who was a beacon of creativity amidst the gritty forwards battle, and he converted brilliantly to give his side a 17-10 half-time lead.
Lamb extended the advantage to 10 points after the restart with an simple penalty, while Tom Arscott’s optimistic attempt from inside his own half fell short.
Ross had better luck soon after, though, bisecting the posts after Welsh won a penalty at a lineout.
It had been a slow start to the half from Saints, hardly hammering home their advantage, but Lamb was able to chalk up another penalty after the pack turned on the power.
Stephen Myler made his return from a hamstring injury soon after, replacing Tom May at full-back but Welsh were soon back to within seven as Ross landed a penalty from halfway.
Saints just held out to end their poor league run and record their sixth win in nine games in the Premiership this season.
Saints: May (Myler 68); K Pisi, Waldouck, Burrell, Elliott; Lamb, Roberts; S Tonga’uiha (A Waller 69), Haywood, Mujati (Doran-Jones 59); Manoa, Lawes (Sorenson 59); Clark, Dowson, van Velze (Oakley 74).
Replacements not used: McMillan, Day, Artemyev.
London Welsh: Arscott; Caprice, Parker, H Tonga’uiha, Scott; Ross, Keats; Montanella (Bateman 65), Briggs (Bristow 65), Ion; Mills, Kulemin (Corker 77); Browne (To’oala 65), Jackson, Balding.
Replacements not used: Tideswell, Stephenson, Davies, Jewell.
Referee: David Rose