USA forward Dempsey scored the the fifth fastest goal in World Cup history after just 29 seconds against Ghana, and is expected to feature for the USA against Portugal despite suffering a nasal fracture in their opening game.
World player of the year Ronaldo is less of a certainty to start in Sunday's pivotal game in Manaus however due to a knee injury. The 29-year-old reportedly ignored doctors' advice to sit out of the remainder of the World Cup, but team-mate Heider Postiga insists that Ronaldo will be fit enough to play on.
"I have already answered so many questions about Cristiano Ronaldo. Actually we speak about him every day. If I am sick of it, imagine how he is feeling," Postiga told to the Associated Press.
"If he is available enough to train with us that's probably because he is feeling well. He's been training with us all these days and as usual he always gives his best. He's just fine."
Ronaldo holds a record 49 goals for his country in 112 senior international appearances, and is 13/5 with Paddy Power to score first in Sunday's match.
The USA will however be without striker Jozy Altidore, who strained his left hamstring against Ghana. Forwards Chris Wondolowski and Aron Johannsson are the top replacements, and Wondolowski told reporters: "It's a big loss losing Jozy, he's been playing really well and is in great form but I think our roles are going to stay the same.
"I know for myself and Aron that we're both going to be ready to play at any minute and just looking for the opportunity and making the most of it whenever we get the chance."
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