The 4-3 victory over Crystal Palace at Deepdale took some pressure off Ferguson, but he conceded he never thought victory was secure - even when his side led by three goals.
"So many good things happened but our defending takes away from that. I don't like ranting and raving. I didn't feel comfortable at 4-1 which is ridiculous. You can't be having free headers from 10-yards in this league," he said.
"Someone's lost concentration and a free header from 12 yards from [Andrew] Dorman changes the game. Everyone was getting tense. We have to be more professional."
Brendan Rodgers, the Swansea City manager, praised the contribution of Marvine Emnes to his side's 2-0 win over Leicester.
The Dutchman joined the Swans on loan from Middlesbrough last week, turning down a move to Glanford Park.
"Marvin knows the system here and he came on and was fantastic," said Rodgers.
"We won the ball back really well, and Darren Pratley's pass for him was exquisite, then Marvin showed great strength and pace to finish terrifically well."
Brian Laws, the Burnley manager, struggled to explain why his side performed so badly in their 4-0 home loss to Reading.
"It's a difficult one to put your finger on, other than to say we've got to be totally honest with ourselves and say we weren't good enough," he said.
"I've also got to give credit to Reading for doing a job on us. I thought there were so many performances that were below par. You can live with one or two, but when it's half a team you get a kick up the backside."
Doncaster Rovers suspect striker Billy Sharp will be out for up to three weeks with the hamstring that forced him out of the win over Sheffield United just before half-time.