The Rovers boss was not happy with his side's ponderous performance against the play-off chasing Addicks.
Rovers had looked on course for defeat after Patrick Bauer's first half header put Charlton into a deserved lead which they never looked like relinquishing.
But Matty Blair headed Rovers level deep into injury time to secure a point.
Ferguson said: "Credit to the players - they kept going and it's a good habit to have that we find a way of getting something out of a game, even if it's only a draw.
"Blair has popped up in injury time and we've done that a few times lately.
"It's not a coincidence, it shows a good character within the team to not know when they're beat.
"That was pleasing that they kept going until the end.
"I thought we were poor today, we didn't have any fluency to what we wanted to do.
"We've gone behind to another set piece, we never got our passing game going.
"There was too many wrong decisions made at the wrong times.
"But I just felt there was too many misplaced passes and not enough rhythm to what we were trying to do.
"It was a bit huff and puff.
"But when you get games like that where it's clearly not one of our better performances, you have to be happy with the result."