The in-form Manchester United winger suffered a shoulder injury
after attempting an acrobatic shot in training on Friday in
Lisbon.
But he still boarded the plane to South Africa and gave a
thumbs-up on his arrival - sparking hopes he would be fine to
play.
He told pals on the flight he would struggle to make Portugal's
friendly with Mozambique yesterday, but was already feeling
better.
But tests showed the injury was worse than first thought. Coach
Carlos Queiroz moved quickly by calling up Benfica midfielder Ruben
Amorim.
Nani, 23, feared he had suffered a dislocated shoulder during
United's Community Shield clash with Chelsea last August but made a
rapid recovery. But there was no such luck this time.
Portuguese FA chiefs said in a statement: "Following the injury
a daily assessment of the damage was made and medical tests
completed. We have concluded he is unable to play
competitively."
Nani is expected to fly back to Manchester in the next few days
and will join England's Rio Ferdinand in the United treatment
room.
Portugal need all the help they can get in the so-called 'Group
of Death' alongside Brazil, Ivory Coast and North Korea.
Nani impressed during the second half of the season for his club
before scoring a spectacular lob in Portugal's friendly against
Cameroon last week.
He is the latest English-based player to suffer World Cup
heartache, following the likes of Chelsea's Michael Essien, Michael
Ballack and John Obi Mikel.
His former United team-mate Cristiano Ronaldo started on the
bench for the 3-0 friendly win over Mozambique at Wanderers cricket
ground in Johannesburg.
Zenit St Petersburg's Danny stepped into Nani's shoes, scoring
one of the goals in a man-of-the-match display.