Per Sportando and Anthony Slater, Serge Ibaka missed Spain's opening game tonight against Iran due to a sore hamstring. Despite some digging, I can find no further relevant information, other than that fellow veteran center Felipe Reyes sat out the game as well.
Still, there is absolutely no reason to panic. The World Cup schedule is ridiculously rigorous, forcing teams to play 5 games in 6 days. Furthermore, Spain's group is extremely top-loaded, with the four top clubs (Spain, Brazil, France, and Serbia) virtually guaranteed to advance. Wasting much energy on Iran or Egypt wouldn't be smart, especially when seeding will be on the line in other contests.
We'll keep an eye on Serge's status as the tournament progresses here at WTLC.