Hull manager Steve Bruce says taking over as Sunderland boss in 2009 was "arguably a mistake" because of his connections with rivals Newcastle.
Bruce, who supported the Magpies as a youngster, was sacked by Sunderland in November 2011 after two years in charge at the Stadium of Light.
Having guided Hull to the Premier League, he faces his former club for the first time on Saturday.
"Looking back on it, going there was arguably a mistake," Bruce said.
"Being where I'm from, being a Newcastle fan as a boy, some would never forgive that."
Bruce joined the Black Cats from Wigan in the summer of 2009 and, after finishing 13th in his first season, Sunderland finished 10th in 2011.
But, after a difficult start, he was sacked three months into the following campaign.
Bruce, who took over as Hull manager in the summer of 2012, added: "I was desperately disappointed after finishing 10th I thought I might have got a bit more time.
"It didn't happen and you move on and thankfully Hull gave me the opportunity to get back to work again.
"When you get sacked you want to come back out fighting and show people what you're about."