Spanish footballer Santiago Cazorla is being kept out of action by a troublesome back injury, it has emerged.

According to goal.com, a medical official at his club Villarreal recently told Spanish newspaper Marca that the 24-year-old midfielder has suffered a slipped disc.

The club has decided not to set a timetable for Cazorla's return, according to team doctor Juan Albors.

"We hope it won't be long but we can't put a date on his recovery, although in theory surgery has been ruled out," he said.

Albors revealed that the player recently visited a specialist clinic for "rehabilitation" treatment on his back.

Cazorla made his debut for Spain in May 2008 and was part of the squad that won the European Championships.

He was also linked with a move to Real Madrid following a series of impressive performances for Villarreal last season.

Physiotherapists often use ultrasound to combat sciatica and other back conditions, as the impact of ultrasonic waves on the muscle tissue can reduce trigger point pain and accelerate healing.