The 25-year-old attacker has refused to commit his future to the Portuguese champions with Chelsea strongly linked with the Brazilian.
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"It is hard to find a player with his characteristics: strength, power, he wins almost every one-on-one situation and can also decide a match with his shots from medium and long range," Dunga told O JOGO.
"He is a player that every club wants because he is different from everyone else."
The former Tokyo Verdy ace, who joined Porto in 2008, has a €100 million (£80m) release clause attached to his contract with the Estadio do Dragao club.