Saints were made to pay for failing to turn possession into points as they suffered a disappointing 28-6 defeat to Wasps on Sunday afternoon.
Jim Mallinder’s men had plenty of the ball, especially during the first period, but they didn’t possess the same kind of sting that their opponents showed.
Saints were only able to muster two Stephen Myler penalties during the match, as Rob Miller’s double and Jamie Stevenson’s late effort earned Wasps a ninth win in their past 10 Aviva Premiership matches.
It leaves Dai Young’s men firmly in the hunt for a top-two spot, while Saints have slipped out of the top four this weekend thanks to Leicester’s bonus-point win against Gloucester.
It means Northampton will need to slay their old foes at Franklin’s Gardens in two weeks’ time as they seek to cut the four-point lead that fourth-placed Tigers now enjoy.
Saints had headed to the Ricoh Arena hoping to at least get back level with their rivals by beating Wasps, and they started strongly, with Myler slotting a penalty from close to halfway.
But Wasps were soon at the Northampton door, with Miller cutting through the visiting defence like a hot knife through butter.
The full-back thought he’d scored, but the TMO deemed that he was just short after being halted by a last-ditch Teimana Harrison tackle.
Wasps then booted a couple of penalties to the corner, but Saints’ defence stayed strong as they won a scrum by stopping the home side’s maul.
Saints were starting to come under increasing pressure though and the concession of a scrum penalty gave Jimmy Gopperth the chance to level the scores, but he hit the left post.
However, he didn’t have to wait long to have another go as another Saints infringement presented an easier kicking chance, which the Wasps fly-half took.
The away side were soon struck with another blow as prop Kieran Brookes was forced off with a head injury after colliding with the knee of Wasps hooker Ashley Johnson.
Paul Hill came on to try to help his team get a foothold in the game, but they continued to huff and puff with Wasps looking the more dangerous.
And when Saints lost possession, George Smith broke free, setting up Thomas Young, whose superb offload sent Miller over for the first try of the match.
Gopperth added the extras to make it 10-3 and Wasps were showing they could sting Saints from any area of the field.
The men in grey needed to summon a response, but they were being met by a black wall at every turn, with Wasps’ defence proving as effective as their attack.
Saints were having so much of the ball in the opposition half, but there was no cutting edge and they were to go in seven points behind at the break.
Saints, who were forced to replace the injured Sam Dickinson with Jon Fisher at half-time, started the second half on the front foot, with Kahn Fotuali’i carrying them forward, but their frustration was further fuelled by the concession of a scrum penalty.
Wasps were winning the eight-man shove and another penalty was earned more than five metres inside their own half.
But the distance didn’t deter centre Elliot Daly, who stepped up and landed a monster effort to draw huge roars from the home faithful.
The sizeable section of Saints supporters were doing their best to rally their troops and they soon had a scrum penalty to shout about, with Myler registering the three points.
Saints were still enjoying plenty of possession, but errors were costing them and so was the concession of penalties.
Daly tried to deliver another huge effort, but he didn’t have enough power to make it two from two from the tee and Saints breathed a sigh of relief.
But they were hit with another injury blow soon after as skipper Lee Dickson, who had come on for Fotuali’i, was forced off with a head knock that initially required lengthy treatment.
That meant Ben Foden was moved to play at scrum-half, with Tom Collins on at full-back and after Collins was put under pressure, Wasps won a penalty and went for the corner.
But their lineout, which had been faltering all afternoon, let them down once more, giving Saints the chance to clear.
It was only to be a temporary reprieve though as Miller again found himself clear of the defence and he dived over to score a crucial try.
Gopperth converted to make it a 14-point advantage and Wasps had their tails up, seeking to completely finish off Saints in the final 10 minutes.
And that was what they did as another long-distance Daly penalty and a late Stevenson effort rubbed salt in the wounds.
Wasps: Miller; Wade, Daly, S Piutau, Halai; Gopperth, Hampson (Stevenson 65); Mullan (c), Johnson (Festuccia 50), Cooper-Woolley (Cittadini 65); Launchbury, Davies (Myall 61); Young (Haskell 56), Smith, Hughes.
Saints: Foden; K Pisi, G Pisi, Mallinder, North; Myler (Hanrahan 71), Fotuali’i (Dickson 54 (Collins 62)); A Waller (Ma’afu 68), Haywood (Marshall 68), Brookes (Hill 19); Lawes, Day (Craig 61); Wood (c), Harrison, Dickinson (Fisher 40).
Referee: Luke Pearce