Watford striker Troy Deeney will sign a new contract in the next 24 hours, Sky sources understand.
Barcelona have reached a preliminary agreement with Sao Paulo to sign Brazilian defender Douglas.
The full-back has signed an deal until the summer of 2014 with the npower Championship table-toppers after leaving Carrow Road earlier this month by mutual consent.
The 30-year-old was previously with the Bluebirds from November until January 1 on loan from the Barclays Premier League side and he made two appearances during his temporary stay in south Wales.
"I'm absolutely delighted to be signing for Cardiff City on a permanent deal and pleased that we've now finalised everything," he told Cardiff City Player.
"I'm looking forward to the rest of the season now and hopefully we can continue the good form we've been showing the past couple of months.
"I thoroughly enjoyed my loan spell here with a great squad of lads. The manager, staff and everyone at the club have been fantastic with me and when I heard they wanted me back here on a permanent deal it was an easy decision to return."