Palace have had an offer for Millwall defender Darren Ward accepted, and the centre-back looks set to sign later this week.
A fee of around £1.1 million has been negotiated, and the player has only to complete a few formalities before joining the Eagles.
Millwall chairman Jeff Burnige revealed he had hoped to keep hold of the 26-year-old, but that Ward was determined on a move to Selhurst Park.
"I made it abundantly clear to Darren, his advisors and many enquiring clubs that Millwall were not seeking to make him available for transfer," Burnige said on Millwall’s website.
"Despite our position, at the end of last week, it emerged that at least three clubs were considering bids of around £1 million. One of these was a Premiership club, and Darren seemed quite determined to move on.
"At the last minute, Crystal Palace made their offer, which threw a spanner in the works, to say the least.
"I am sure that all Millwall fans would have preferred him to move to a Premiership club, and certainly not to one of our fiercest rivals.
"However, once Darren had made his decision, the board had to accept the situation and the fee agreed represents good business for our club."