Ben Tozer scored from close range to put the Cobblers ahead but Peter Vincenti turned the ball home at the far post to equalise. Shaun Harrad received a straight red for kicking out at the Shots' Anthony Charles late on.
Sampson said: "I thought we'd got over our poor performance of Tuesday night when we took the lead."
He added: "They're all good players here and we've got to stick to our principles, to keep passing the ball.
"If we do I'm sure the players will improve but at the moment our ball execution is not good enough.
"It's no use the players hiding, they've got to keep wanting the ball because that's the way I want to play and my principles of football are not going to change."
Source: PA
Source: PA