Chelsea's Antonio Rudiger says "difficult" contract negotiations and a lack of communication are the reasons behind his departure from the club.
The defender, whose deal with the Blues expires this summer, was offered a contract worth more than £200,000 to stay at Chelsea.
However, Real Madrid have agreed a deal to sign the Germany international.
"I leave this club with a heavy heart. It has meant everything to me," Rudiger told The Players' Tribune.
"Unfortunately, my contract negotiations had already started to get difficult last fall.
"Business is business, but when you don't hear any news from the club from August to January, the situation becomes complicated."
Rudiger, who joined Chelsea for an initial £29m from Roma in 2017, is expected to sign a four-year deal at the Bernabeu.
He has made over 200 appearances for Chelsea, winning the Champions League, Europa League, Club World Cup and the FA Cup.
"We're not robots, you know? You cannot wait for months with so much uncertainty about your future," he said.
"Obviously, no one saw the sanctions coming, but in the end, other big clubs were showing interest, and I had to make a decision."
With Blues owner Roman Abramovich sanctioned by the UK Government over Russia's invasion of Ukraine, Chelsea cannot currently buy or sell players, or renew contracts with players they already own.
It is understood the contract offer to Rudiger was made weeks before the imposition of the sanctions, which put player contract deals on hold until the end of May when the government is expected to issue the club with a special licence.
The club are also set to lose Danish centre-back Andreas Christensen this summer to Barcelona on a free transfer, but captain Cesar Azpilicueta is expected to stay after a one-year extension was triggered in his contract earlier this season.
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