Simply put, should the United States beat Portugal on Sunday in Manaus they will lock up a spot in the Round of 16 for a second straight World Cup.

Following their 2-1 win over Ghana, the U.S. is currently second in Group G with three points, but could leapfrog Germany for first place and eliminate Portugal with a victory.

But the U.S. and manager Jurgen Klinsmann may need many things to fall their way if they hope to advance.

Is Ronaldo going to be effective?

Portugal is also seeking a return to the knockout stage, but many questions still surround superstar forward and all-time leading scorer Cristiano Ronaldo.

The 29-year-old Real Madrid scoring machine wore a brace on his left knee throughout training prior to the match, and his health may run parallel to Portugal’s success.

Ronaldo’s game is built around his speed and physical presence, and he’s especially lethal from the air off set pieces. Ronaldo at 50 percent is still better than most players in the world, but his shaky knee gives the U.S. an advantage.

Can the U.S. forwards score without Jozy Altidore?

The young striker is out after suffering a hamstring injury early in the Ghana win, and his absence creates a huge hole in the Yanks attack.

Altidore is second on the team with 23 goals in 71 career appearances, and his overpowering game could have done wonders for the U.S. against Portugal and Germany.

The pressure to score will fall mostly on Clint Dempsey, but he’ll need help from Aron Johannsson and Chris Wondolowski. Both should see the pitch at some point Sunday, with Johannsson the most likely to score with his stronger technical and dribbling skills.

Will Portugal’s defense suffer without Pepe, Fabio Coentrao?

The heart of Portugal’s backline will miss defender Fabio Coentrao due to injury, and Pepe to suspension after the Real Madrid star head-butted an opposing player in the 4-0 loss to Germany.

Combined, Pepe and Coentrao have 105 career appearances and seven goals for Portugal, but Paulo Bento’s side does have some depth and experience to rely on. Bruno Alves is the most experienced player on Portugal’s side after Ronaldo with 73 caps and 10 goals, and Joao Pereira is capable of helping out in the backline or moving up to aid the attack.

Michael Bradley to rebound from lackluster game against Ghana?

Overall, Ghana got the best of the U.S. in every facet except for the scoreboard, and the Yanks will need better, more consistent play from central midfielder Michael Bradley. Ghana held a 59-41 possession advantage, forced seven corner kicks and generated 21 total shots with eight on target, and improvement from Bradley could swing some of those stats in the Yanks' favor.

Bradley couldn’t squeeze off a shot and was largely outplayed by Ghana’s more athletic midfielders. His role in Klinsmann’s system is that of facilitator, but Bradley needs to assert himself more on the ball for the U.S. to be successful

More U.S. heroics?

Dempsey provided the opening goal in the first 30 seconds, but the U.S. did lose control late against Ghana when fatigue set in, which led to defender John Brooks entering and providing his surprise goal.

Brooks may not see the pitch again during this Cup, but another unlikely hero might be young midfielder Julian Green or veteran wingback DaMarcus Beasley. Green, 19, has only made two international appearances but if the U.S. attack struggles he may be tapped for some instant offense.

Start Time: 6 p.m. EST

TV Channel: ESPN

Live Online Stream: A live stream is available at Watch ESPN here.