Adriano missed a penalty at the weekend as Flamengo lost the final of the second phase of the Carioca (Rio) state championship, handing the title to winners Botafogo.
The former Inter Milan striker, top scorer last year when Flamengo won the Brazilian championship, has struggled for form and with off-field issues this year he has made only 12 out of a possible 23 appearances for the club.
Flamengo play Caracas FC at the Maracana on Wednesday in a Libertadores Cup match that will decide if they reach the knockout phase of South America's premier club competition.
Adriano, who recently recovered from a rib injury, also has Flamengo's opening game of the Brazilian championship against Sao Paulo on May 9 before Dunga's squad gather to prepare for the World Cup.
"I'd never missed a penalty and it had to happen now," exclaimed Adriano after Sunday's defeat.
Had Flamengo won on Sunday the Carioca championship would have gone into a two-leg final between the winners of the two phases, guaranteeing Adriano two more matches this month. Botafogo won both phases avoiding the need for a play-off.
Adriano returned home from Inter a year ago to escape off-field problems he had in Italy and almost quit football before recovering his best form with Flamengo.
He played in Brazil's only friendly this year, a win over Ireland in London, but did not impress. On his return from London he missed a Flamengo practice and media reported an argument with his model girlfriend and suggested a drink problem was the cause.
"Adriano is lucky because at the moment there is no other striker with the same characteristics to fight for a place in the national team," said former Brazil World Cup left-back Junior, now a media pundit.
"He has a lot of credit with the coaching staff and that's why I think he's guaranteed a place at the Cup. Then there's a month's preparation and there anyone can get into shape," the 55-year-old told Reuters.
Adriano had said before Sunday's match he knew defeat would bring his non-footballing issues back to the surface "but I'm well prepared, that's not going to take me down."
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