The visitors were outclassed en route to a club record 10th straight defeat in all competitions. Here are our player ratings from South Wales...
5. Nesta Guinness-Walker
Often one of the team's better performers even on bad days but had his struggles here. Left Tanner unmarked to set Cardiff on their way after only nine minutes and was bewildered by Colwill's movement for the second. Improved when moved to the right in the second half and did well for Evans' goal... 5 Photo: Pete Norton
6. Dean Campbell
Totally overrun and overwhelmed by his midfield counterparts. Never able to establish any foothold or curb Cardiff's dominance, though it's not as if he was given much support... 4.5 Photo: Pete Norton
7. Cameron McGeehan
Twice threatened in the opening five minutes but spent the rest of the first half chasing shadows. Good pressing to create the consolation... 4.5 Photo: Pete Norton
8. Tyrese Fornah
The lack of intensity and aggression in his defending made it way, way too easy for Willock to create space and cross for the first goal. That was the last thing Cobblers needed and it set the tone for the rest of the game. He never recovered... 3.5 Photo: Pete Norton