Manuel Pellegrini has been faced with an injury concern in some capacity all season, with long-term absentee Nihat Kahveci still crocked with a thigh injury.
Now Uruguayan international Diego Godin has returned from international duty with a thigh strain in his left leg, giving the Chilean coach another selection headache.
Godin picked up the knock in the first half of Uruguay's hard-fought 0-0 draw with France in the Stade de France on Wednesday evening, and was immediately replaced by team-mate Valdez, such was the extent of the injury.
The 22-year-old has been in impressive form for Los Submarinos Amarillos this season, making ten appearances in La Liga and three in the Champions League. His partnership with Gonzalo at the back has been the cornerstone of the club's impressive start to the season, so his absence will be a huge loss.
Pellegrini suffered another blow earlier in the week as prolific forward Joseba Llorente was ruled out for month with a muscle injury of his own, making Guille Franco and Giuseppe Rossi the only two fully fit senior strikers at the club.
Young American Jozy Altidore could see more action as Villarreal may struggle to cope with a tough run of fixtures in December.
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