Barcelona coach Pep Guardiola was admitted to hospital overnight for treatment on his back problem.
Guardiola has been suffering from acute lower back pain for the last few weeks but the problem has worsened in recent days and he was unable to attend team training on Tuesday.
Guardiola, 40, sat on the Barca bench for Wednesday night's 1-0 league victory at Valencia, but the post-match press conference was taken by his assistant Tito Vilanova. Guardiola will again be missing for today's training session.
Barca, who provisionally moved 10 points clear of second-placed Real Madrid in the Primera Division table with their win at the Mestalla, play Real Zaragoza this weekend at the Nou Camp before next week hosting Arsenal in the second leg of their Champions League last-16 tie, where they will look to overturn a 2-1 deficit from the first leg.
Guardiola has been diagnosed as suffering from a herniated disc, Barcelona confirmed on their website.
A statement read: "Early this morning, Guardiola was admitted to hospital in Barcelona to continue treatment and study of his acute back pain. His medical examination has revealed that he has a herniated disc, and he will be treated with drugs and epidural injections. His release from hospital depends on the progress he makes."
