Alonso completed a medical this afternoon and will join up with the squad officially when the transfer window opens.
And as such, has been sent out to the Premier League club until the end of the season.
“I was looking for a player in that position on the left side and I hope he will help us," manager Gus Poyet told the BBC.
"I am delighted that everything is agreed.”
Sunderland have com21点官网pleted the signing of Fiorentina六合投注网站> defender Marcos Alonso on a six-month loan deal.
The Spanish full-back has found first team football hard to come by at the Stadio Artemio Franchi this season.