Newcastle midfielder Jack Colback can win over doubters with his performances after moving from rivals Sunderland, according to Lee Clark.
Magpies fan Colback, 24, ended 16 years on Wearside by moving to Newcastle.
Former midfielder Clark made the move in the opposite direction in 1997, helping Sunderland into the Premier League during a two-year stay.
"Even my staunchest critic would admit when it came to doing the business, I did," Clark told BBC Newcastle.
"Ultimately it's down to Jack coming in and continuing where he left off at Sunderland.
"He's looked a good player, he's a Newcastle fan, you're excited by his signing and he can add something to the team."
Colback scored for Sunderland against Newcastle in the last of his seven Tyne-Wear derby appearances - a 3-0 victory at St James' Park in February - but will line up on the other side of the divide for the first time next season.
Birmingham City manager Clark scored 16 goals in 85 appearances for Sunderland, helping them to win the First Division title in 1999. He left the club after he was pictured in a T-shirt sporting a derogatory slogan about them.
But the 41-year-old felt he always had a positive relationship with fans of both sides.
"I had no problems at all," Clark continued.
"When I was playing for Sunderland, I would go back to St James' Park to watch Newcastle. I never had any issues with anyone.
"There was a bit of friendly banter at worst from the Newcastle fans, and the support from the Sunderland fans was fantastic.
"Take away all the hullaballoo about it, it's ultimately like any player. It doesn't matter where he comes from, it's what they do on the pitch that they'll be judged on."