Swansea chairman Huw Jenkins says they reluctantly sold Ashley Williams to Everton after the defender asked the Welsh club to allow him to move on.
The Wales international ended an eight-year association with the Swans on Wednesday when he joined Ronald Koeman's side on a three-year deal for an undisclosed fee.
Williams had been a pillar at the back for the team since they won promotion to the Championship in 2008, racking up 352 appearances in all competitions, and Huw expressed his disappointment at seeing the 31-year-old centre-back leave the Liberty Stadium.
"We are disappointed to lose Ashley. It is definitely not something we wanted to happen," Huw told the club's official website.
"But having turned down Everton's initial offer, Ashley expressed his desire for a new challenge at this time of his career.
"Taking into account the excellent service Ashley has given this football club over the last eight years, including as club captain, we reluctantly agreed to his request to join Everton after they made an improved offer.
"It goes without saying that we wish him the very best with his new challenge and thank him for his services."
Williams moves to Goodison Park as a replacement for John Stones, who was sold to Manchester City on Tuesday for a fee that could rise up to £50 million.