Marcos, a member of Brazil's 2002 World Cup winning team, suffered the injury in a 4-1 win over Juventus. He left the game in the first half.

He is now expected to wear a cast on the arm, keeping him out of action for the long term.

"His arm will be immobilised for six weeks and then he'll need physiotherapy," Palmeiras doctor Rubens Sampaio said.

"It will take at least two months before he can practice with the rest of the team again."

The 33-year-old goalkeeper suffered the fracture in what appeared an innocuous collision with Juventus defender Reginaldo.

"It was a header to the forearm," Marcos said. "It's just unfortunate. I jumped up to catch the ball and broke it."

Sampaio added: "I've known Marcos for ten years and this is the most upset I have seen him."

Marcos' Palmeiras team-mates are offering their veteran goalkeeper plenty of support as he faces a lengthy spell on the sidelines.

"It's a pity," coach Caio Junior said. "Now we have to help him a lot.

"We'll find things for him to do so he doesn't become too downcast. He is a very important player, but even more important as a person."

Striker Edmundo added: "Marcos is a bit pessimistic, thinking that whatever it happens to him, it will be forever. I hope he can be with us as soon as possible because he is a fantastic guy."