Andy Holt earned a point for Town with a late equaliser but Sampson saw a missed opportunity for his side to maintain their play-off charge.
He told BBC Radio Northampton: "Very scrappy and disjointed at the start, not too pleased with that.
"But in the last 30 minutes, the lads decided to get it down and play, and we don't look a bad team.
"(Stephen) O'Flynn has a physical presence and we probably missed that in the first half."
Cobblers now lie 13th in League Two, five points off a top-six spot.