Pep Guardiola admitted to hospital after Barcelona victory

Wednesday's 1-0 reverse was the first defeat Pep Guardiola has suffered against Real Madrid since taking over in 2008 (GETTY IMAGES)

Barcelona coach Pep Guardiola was admitted to hospital overnight for treatment on acute lower back pain, the La Liga club said today.

The 40-year-old former Barca and Spain midfielder had to cancel a news conference on Tuesday because of the complaint and looked in pain during the champions' 1-0 win at Valencia on Wednesday.

"Pep is not feeling great and he got through the match as best he could," Guardiola's assistant, Tito Vilanova, said at a news conference after the game at the Mestalla.

"He is having a bad time of it and he doesn't even know where to put himself."

Guardiola's back problem comes at a crucial time for the Spanish champions.

They have away matches at Sevilla and Villarreal in coming weeks and will attempt to overturn a 2-1 deficit against English club Arsenal in their Champions League last-16, second leg at the Nou Camp on Tuesday.