Blackpool boss Lee Clark has signed Manchester United midfielder Joe Rothwell on loan until the end of the season.
Newcastle midfielder Moussa Sissoko is happy to stay at the club, despite rumours he is a target for Arsenal.
The Spanish club, also owned by Watford supremos the Pozzo family, confirmed on their website that Iriney has agreed a season-long deal at Vicarage Road.
The 32-year-old has spent more than 10 years in Spain and also played for Rayo Vallecano, Celta Vigo, Real Betis and Almeria.
Watford caused controversy last season by bringing in a host of loanees from Granada and the other Pozzo-owned club, Udinese.