Centre back Giorgio Chiellini has left the Italian squad after suffering a calf injury in training, dealing a blow to Italy a day before their crucial World Cup qualifier against Spain.

The Juventus defender is on his way to Turin to treat the injury with medical staff at his club, the Italian Soccer Federation said on Friday, and has been ruled out of the game with Spain and Tuesday's qualifier at home to Israel.

Spain and Italy are locked on 16 points at the top of Group G with four games remaining. They have won every game so far aside from their 1-1 draw in Turin last October, although Spain lead the group due to their superior goal difference.

Chiellini also missed the qualifier with Spain last October with an injury. Juventus defender Daniele Rugani is expected to take his place at centre back.

"Italy are a great side, not just in defence, although they have always been renowned for being solid and difficult to beat, but they also have a lot of quality in attack," Spain captain Sergio Ramos told a news conference on Friday.

"Tomorrow so much is at stake, we're playing for the right to be at the World Cup, but we're at home, at the Bernabeu, which is an imposing stadium and I'm sure we'll have a lot of support.

"It's going to be a special day for football fans, it's one of the best games to see in the world, but we'll try and stick with our usual playing philosophy to try and get the three points."