Roy Keane has warned Sunderland supporters that he “won't tolerate” a repeat of the abuse he received during the narrow Carling Cup victory over Northampton Town. After two largely harmonious years of improvement at the Stadium of Light, the manager served notice on a vocal minority of fans “with short memories” that personal insults are strictly off limits.

While there is no sense that the Irishman is considering his position on Wearside, he is well inside the final season of his contract at Sunderland and his comments will be studied with interest. Unpredictability remains a defining feature of Keane's management style, while complacency is a quality that he will not accept. Respect, whether towards officials or the badge, is another requirement.

Having made eight changes to the side who beat Middlesbrough on Saturday, Keane was apoplectic about his reshaped team's display in the match against Northampton, of Coca-Cola League One, in which Anthony Stokes scored two late goals to force the tie into extra time. Sunderland won on penalties, but Keane reflected later on “one of the worst nights I've experienced in my football career.”

The manager spread his anger freely, encompassing the small number of fans who aimed invective at the dugout on Tuesday night. While his team selections and substitutions do not always meet with universal approval and his record in knockout competitions is patchy, when he took the job in August 2006, Sunderland were at the foot of the Coca-Cola Championship table. They are now eighth in the Barclays Premier League.

“The abuse of one or two supporters is something I won't tolerate,” Keane said. “Some were targeting me. I won't go into it, but that's something I've not come into the job to accept. I appreciate criticism, the constructive criticism which I am going to receive. Trust me, my biggest critic is myself. I know the abuse is part of football, but it's something I won't tolerate.”

Keane was angry at himself for not taking the opportunity to blood youthful players against Northampton. “I keep talking about these good young players coming through and I should have played one or two,” he said. “At least they run and sprint and tackle. They want to make a career at Sunderland. I regret that. International players came in and there were more on the bench; they had the chance and some didn't take it.”