Zaragoza director Erard Poschner claims they are disappointed with the impact made by Pennant and are ready to sell him back to the Premier League next month, if they can find a buyer.
"We are disappointed with Pennant. This is based on the commitment of the players," Poschner is quoted as saying in The Sun.
"With spirit like this it is better to 'sack' some players and seek reinforcements in the winter market. We want players who guarantee their work and effort."
The Hammers, as well as Aston Villa, have been linked with a move for the former Birmingham man who recently expressed his happiness with life in Spain.