England goalkeeper Fraser Forster does not know if he will still be at Celtic when they next play in Europe.
Norwich captain Sebastien Bassong has signed a new two-and-a-half-year contract.
The Blanquillos finished rock bottom of the Primera Division - albeit just three points adrift of 17th-placed Celta de Vigo - with previous boss Manolo Jimenez paying the price for the setback earlier this week.
Zaragoza have turned to former Liverpool assistant Herrera, who has managed a host of Segunda Division sides in the past, to guide them back into into the top flight.
The 59-year-old has signed a two-year deal.