Benfica's Portuguese international midfielder Ruben Amorim is likely to be out of action for up to six months after rupturing knee ligaments during his side's 1-0 win over league rivals Boavista at the weekend, the club announced on Monday.

The 29-year-old, who has made 14 appearances for Portugal, is set to undergo sugery this week in Lisbon, after breaking down in the 32nd minute of Benfica's second straight win of the season on Sunday.

Amorim was part of Paulo Bento's World Cup squad in Brazil, where Portugal were knocked out in the first round, and played in the 2-1 final group match win over Ghana.