Fourteen-man Saints tame Tigers
Northampton captain Dylan Hartley could be suspended for the start of England's Six Nations campaign after he was sent off for elbowing an opponent in his side's 23-19 win over Leicester on Saturday.
Hartley's career has been marred by disciplinary problems, including a 26-week ban for eye-gouging in 2007 and an 11-week suspension for verbally abusing referee Wayne Barnes during the 2013 Premiership final.
He was banned for the British and Irish Lions tour of Australia as a result of last year's incident and Rugby Football Union chiefs could take a dim view of his latest indiscretion in a hard-fought Premiership clash at Franklin's Gardens.
Referee JP Doyle seemed happy to award a yellow card when Hartley's elbow caught Tigers centre Matt Smith in the face in the 17th minute.
As Smith fell to the ground, a brawl broke out involving several players, but television match official Sean Davey urged Doyle to watch further replays, and he responded by sending 61 times-capped Hartley off.
England open their Six Nations campaign against Wales in Cardiff on February 6, and, given Hartley's poor disciplinary record, another lengthy suspension appears likely, with a disciplinary hearing set to be convened before Christmas.
"It was disappointing," Northampton rugby director Jim Mallinder said.
"Dylan has got to keep his arms down, but he was being held and I don't know there was any malice in it.
"The nature of the game didn't justify a red card. I think Smith went down pretty easily, to be honest, which was disappointing."
Hartley's dismissal took the gloss off a win that kept Northampton top of the Premiership thanks to substitute Jamie Elliott's 77th-minute try which flyhalf Stephen Myler converted from the touchline.
Saints had earlier delivered tries for prop Alex Waller and replacement Ben Foden, plus two Myler penalties, with the lead changing hands five times during the second half.
*Elsewhere, second placed Bath kept the pressure on Northampton with a 39-16 win at Gloucester.
*Fourth-placed Saracens got back on track as they scored 11 tries in a 78-7 rout of London Welsh.
Mark McCall's men had not secured a league victory for more than two months.
But they did not give Welsh a sniff at Allianz Park, as Mako Vunipola, who grabbed two tries, Brett Sharman, George Kruis and Chris Ashton all crossed in the firsthalf.
Elliot Kear did respond for the Exiles but Sarries made the scoreline even more emphatic as replacement Richard Wigglesworth grabbed a hat-trick of tries, in addition to scores from Jackson Wray, Richard Barrington and Ben Ransom.
*Five penalties from Tim Swiel saved Harlequins from a surprise home defeat at the Stoop as they edged strugglers Newcastle Falcons 15-7.
All Saturday's scores and scorers
Harlequins 15-7 Newcastle Falcons
For Harlequins:
Pens: Swiel 5
For Falcons:
Try: Tuilagi
Con: Socino
The teams:
Harlequins: 15 Mike Brown, 14 Marland Yarde, 13 Matt Hopper, 12 George Lowe, 11 Aseli Tikoirotuma, 10 Tim Swiel, 9 Karl Dickson, 8 James Chisholm, 7 Jack Clifford, 6 Joe Trayfoot, 5 George Robson (captain), 4 Charlie Matthews, 3 Kyle Sinckler, 2 Joe Gray, 1 Mark Lambert.
Replacements: 16 Dave Ward, 17 Darryl Marfo, 18 Will Collier, 19 Sam Twomey, 20 George Merrick, 21 Danny Care, 22 Ross Chisholm, 23 Ugo Monye.
Newcastle Falcons: 15 Simon Hammersley, 14 Sinoti Sinoti, 13 Adam Powell, 12 Juan Pablo Socino, 11 Alex Tuilagi, 10 Tom Catterick, 9 Mike Blair, 8 All Hogg, 7 Will Welch (captain), 6 Mark Wilson, 5 Dom Barrow, 4 Calum Green, 3 Scott Wilson, 2 George McGuigan, 1 Rob Vickers.
Replacements: 16 Scott Lawson, 17 Eric Fry, 18 Mark Irving, 19 Kane Thompson, 20 Josh Furno, 21 Ruki Tipuna, 22 Andy Tuilagi, 23 Noah Cato.
Saracens 78-7 London Welsh
For Saracens:
Tries: Vunipola 2, Sharman, Kruis, Wray, Ashton, Ransom, Wigglesworth 3, Barrington
Cons: Farrell 10
Pens: Farrell
For London Welsh:
Try: Kear
Con: Robinson
Yellow cards: Peter Browne (London Welsh, 50), Lachlan McCaffrey (London Welsh, 80)
The teams:
Saracens: 15 Ben Ransom, 14 Chris Ashton, 13 Marcelo Bosch, 12 Duncan Taylor, 11 Chris Wyles, 10 Owen Farrell, 9 Neil De Kock, 8 Ernst Joubert (captain) 7 Kelly Brown, 6 Jackson Wray, 5 Jim Hamilton, 4 George Kruis, 3 James Johnston, 2 Brett Sharman, 1 Mako Vunipola.
Replacements: 16 Jamie George, 17 Richard Barrington, 18 Petrus Du Plessis, 19 Mouritz Botha, 20 Billy Vunipola, 21 Richard Wigglesworth, 22 Charlie Hodgson, 23 Nick Tompkins.
London Welsh: 15 Will Robinson, 14 Seb Stegmann, 13 Nic Reynolds, 12 Olly Barkley, 11 Elliot Kear, 10 Piri Weepu, 9 Rob Lewis, 8 Opeti Fonua, 7 Carl Kirwan (captain), 6 Lachlan McCaffrey, 5 James Down, 4 Peter Browne, 3 Taione Vea, 2 Koree Britton, 1 Rickey Reeves.
Replacements: 16 Nathan Morris, 17 Nathan Trevett, 18 Ben Cooper, 19 Dean Schofield, 20 Ben Pienaar, 21 Paul Rowley, 22 Tom May, 23 Nick Scott.
Northampton Saints 23-19 Leicester Tigers
For Northampton:
Tries: Waller, Elliot, Foden
Con: Myler
Pens: Myler 2
For Leicester:
Tries: Goneva 2, penalty try
Cons: Williams, Burns
Yellow card: Tom Croft (Leicester, 38)
The teams:
Northampton Saints: 15 James Wilson, 14 Ken Pisi, 13 Tom Stephenson, 12 Luther Burrell, 11 George North, 10 Stephen Myler, 9 Kahn Fotuali'i, 8 Samu Manoa, 7 Tom Wood, 6 Calum Clark, 5 Christian Day, 4 Courtney Lawes, 3 Salesi Ma'afu, 2 Dylan Hartley (captain), 1 Alex Waller.
Replacements: 16 Mike Haywood, 17 Ethan Waller, 18 Gareth Denman, 19 Sam Dickinson, 20 Phil Dowson, 21 Lee Dickson, 22 Jamie Elliott, 23 Ben Foden.
Leicester Tigers: 15 Mathew Tait, 14 Blaine Scully, 13 Matt Smith, 12 Anthony Allen, 11 Vereniki Goneva, 10 Owen Williams, 9 Ben Youngs (captain), 8 Jordan Crane, 7 Julian Salvi, 6 Tom Croft, 5 Geoff Parling, 4 Graham Kitchener, 3 Dan Cole, 2 Tom Youngs, 1 Marcos Ayerza.
Replacements: 16 Leonardo Ghiraldini, 17 Fraser Balmain, 18 Michele Rizzo, 19 Sebastian De Chaves, 20 Robert Barbieri, 21 Sam Harrison, 22 Freddie Burns, 23 Miles Benjamin.
Gloucester 16-39 Bath
For Gloucester:
Try: Robson
Con: Hook
Pens: Laidlaw 3
For Bath:
Tries: Garvey 2, penalty try
Cons: Ford 3
Pens: Ford 6
Yellow card: Sila Puafisi (Gloucester, 55)
The teams:
Gloucester: 15 Steve McColl, 14 Charlie Sharples, 13 Henry Purdy, 12 Billy Twelvetrees (captain), 11 Jonny May, 10 James Hook, 9 Greig Laidlaw, 8 Ross Moriarty, 7 Matt Kvesic, 6 Sione Kalamafoni, 5 Tom Palmer, 4 Tom Savage, 3 John Afoa, 2 Richard Hibbard, 1 Yann Thomas.
Replacements: 16 Darren Dawidiuk, 17 Nick Wood, 18 Sila Puafisi, 19 James Hudson, 20 Elliott Stooke, 21 Dan Robson, 22 Mark Atkinson, 23 David Halaifonua
Bath: 15 Anthony Watson, 14 Semesa Rokoduguni, 13 Jonathan Joseph, 12 Kyle Eastmond, 11 Matt Banahan, 10 George Ford, 9 Chris Cook, 8 Leroy Houston, 7 Francois Louw, 6 Alafoti Fa'osiliva, 5 Dominic Day, 4 Stuart Hooper (captain), 3 David Wilson, 2 Ross Batty, 1 Paul James.
Replacements: 16 Rob Webber, 17 Nick Auterac, 18 Henry Thomas, 19 Matt Garvey, 20 Carl Fearns, 21 Micky Young, 22 Ollie Devoto, 23 Sam Burgess.