Alan Solomons gave credit to Saints after his Worcester Warriors side lost 38-10 at Franklin's Gardens on Saturday afternoon.
But the Warriors boss admitted injury issues and the first-half sin-binning of Francois Hougaard had cost his team dear in the Gallagher Premiership clash.
Worcester were hit by four head injury assessments during the match, three of them through the rugged first period when Saints ran amok.
Solomons later said this was the reason for the problems they faced as Saints racked up the points, rather than any lack of ambition in knowing before the match that they were safe from the Premiership drop.
"You have to give credit to Northampton," Solomons said. "They played well and deserved the win but, secondly, the first half was tremendously disruptive.
"We had three HIAs, none of whom came back onto the field.
"Then we lost Francois Hougaard to a yellow card so we were in real trouble.
"We did well at the end of the first half to get a try and go in 28-10.
"Second half we shored up defensively but lost Gareth (Milasinovich) to another HIA but the lads who came on made the difference.
"Our defence in that second half was miles better."