Aberdeen captain Russell Anderson has completed his £1m move to Premiership newcomers Sunderland.
The 28-year-old's agent, Blair Morgan, said the Scotland international defender travelled south on Wednesday to agree personal terms.
Anderson, who has nine Scotland caps, has signed a three-year deal with the Wearside club.
Aberdeen assistant manager Jimmy Nicholl told BBC Sport that Anderson would be a huge loss to the team.
The defender made his Aberdeen debut under former manager Roy Aitken in 1996 and had his testimonial last season.
Middlesbrough and Everton were also reportedly interested in taking the centre-half to the Premiership.
"We cannot really deny Russell the chance to play against some of the best players in the world"
Aberdeen's director of football Willie Miller confirmed more than one club had been interested in buying the player.
"While it's a blow to lose a player of Russell's ability, we always knew that if he was going to move, it would be to the Premiership," Miller told the club website.
"There was interest from other clubs and another offer on the table, but from a Championship side - and that was knocked back by both the club and the player.
"As part of the deal, Russell was due a fee but he's relinquished that, in order that it goes towards youth development here at Aberdeen."
Miller said the club found it impossible to turn down Sunderland's seven-figure offer.
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"Russell wanted to go and as a club we cannot really deny him the chance to play against some of the best players in the world and challenge that comes with that," Miller added.
"I'm sure the move will also further his international career and everyone here at Pittodrie wishes him well."
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