Gael Kakuta has joined Rayo Vallecano on loan from Chelsea, the Spanish club have announced.
Werder Bremen's Thomas Eichin says any clubs interested in striker Davie Selke can "save themselves the phone call".
The 21-year-old had over a year left to run on his existing deal but the club were keen to tie him to a longer-term agreement.
Alfei, who has spent most of the season on loan at Wrexham, said: "I'm absolutely delighted. It's good to know the club has faith in me and there is nowhere I would rather be than Swansea."