Rovers fell behind after 24 seconds and faced an uphill battle from there against a Northampton outfit who had failed to pick up a single point in their previous four league matches.
Ferguson’s side were particularly poor in the first half and although there was a modicum of improvement after the break, they could not break Northampton down.
“We spoke about the way they would start, with a new manager coming in, lifting the crowd and we made the worst possible start to the game,” said manager Ferguson, after Matt Crooks’ early strike.
“After that we couldn’t frustrate them like we wanted to. We had a lot of the ball and didn’t do enough with it.
“We weren’t quick with it, didn’t move it quick enough, play it forward quick enough. So, it was a really disappointing day.
“That’s four blanks out of six matches now and it’s an issue that has to be sorted.
“The second half was better. The last 15 minutes in particular there was a real urgency to our game. If we played like that the whole game then the outcome would be different. But it was nowhere near.
“For 20 minutes of the first half we got complete control of the game, but we only had two shots. It’s not how I want us to play. I have to reflect on it and look at it again.”
Northampton Town: Ingram, Taylor, Smith (Powell 88), Pierre, Moloney, Crooks (Richards 76), McWilliams, Grimes, Buchanan, Long (Waters 57), Revell. Unused substitutes: Cornell, Kasim, Barnett, Poole.
Doncaster Rovers: Lawlor, Blair, Wright, Butler, Toffolo (Coppinger 46), Kongolo, Whiteman, Rowe, Garrett (Houghton 60), Marquis, Mandeville (May 61). Unused substitutes: Alcock, Mason, Williams, Marosi.
Referee: D Handley (Lancashire).