Having already equaled its best finish in the Copa America, the United States faces the biggest challenge that can be put to any team: stopping five-time World Player of the year and Argentine talisman Lionel Messi.

Even though Messi has yet to claim a major crown on the international stage, the 29-year-old Barcelona superstar is widely considered the best in the world and he’s certainly played that way throughout the Centenario. He is second in goals (four), and has two assists following Argentina’s 4-1 quarterfinals victory over Venezuela. In 111 international appearances with Argentina’s senior team, Messi’s overpowered all comers for 54 goals, having just tied all-time great Gabriel Batistuta for the nation’s lead.

But the U.S. may have the hard-nosed tandem in central defense to slow the prolific scorer and playmaker, with defenders Geoff Cameron and John Brooks stepping up in this year’s tournament.

Through four matches, including last week’s 2-1 quarterfinals triumph over Ecuador, the Yanks have allowed a mere three goals over four matches with the emerging 23-year-old Brooks leading all defenders with 30 clearances and Cameron notching 18, the third-best total, according to ESPNFC.

Brooks, who rediscovered his form after poor showings at the Gold Cup, said the quick turnaround from his club season with Bundesliga’s Hertha BSC to the Copa America helped him develop. Throughout the tournament, Brooks has made some exceptional tackles, and his 6-foot-4 frame could be crucial for preventing Argentina from scoring on set pieces.

"For me, the key was that I played a lot of games at my club, and then I came here and I was very confident," Brooks told ESPNFC after beating Ecuador. "It just keeps going."

Stoke City’s Cameron, who’s seven years Brooks' senior, lavished Brooks with praise and mentioned how their skill sets intertwine earlier this month.

"I really enjoy playing alongside of [Brooks]," Cameron said earlier this month. "There's times where I use my speed and my strength to cut out a pass, but I don't have to do that as much because he's got that speed and he's got the strength. He's powerful. He's got the ability and the skill set that a lot of people should admire."

Cameron has been a steady force for the U.S. after some quality performances in the Premier League. He has been a consistent starter with Stoke, and his strong knowledge of the game has proven invaluable to a side that often has cohesion issues due to U.S. head coach Jurgen Klinsmann's multiple lineups.

Should the U.S. midfield breakdown, a likely occurrence given Messi’s lightning quick feet and in comparable dribbling skill, Brooks and Cameron can thwart Messi long enough to allow keeper Brad Guzan time to position for that famous left foot.

Guzan can also be viewed as a key player against the Messi defense. After some struggles with Aston Villa, the 31-year-old has filled in well for great Tim Howard, recording 16 saves over his four starts.

Klinsmann, ever the pragmatist, believes the his side can approach the Messi situation much like it did against Portugal’s Cristiano Ronaldo at World Cup group stages two years ago. The Real Madrid star and long-time rival of Messi, was held scoreless, but did assist the stunning equalizer in the closing seconds of stoppage time.

"We take it as it comes," Klinsmann said. "There is no need to talk and make Argentina bigger than they are. We played two years ago (against) Ronaldo and that was a big game, too. We were winning 2-1 right into the 96th minute. We came so far now and we are hungry for the next step, even though we understand it is a big opponent."

Few players are more clever with the ball than Messi, and it will be up to Klinsmann's defense to deny the Barcelona superstar from finding room to unleash a shot from distance, penetrate as he so skillfully does into the box or not foul him as he works his dribbling magic. It's a tough task, but Brooks and Cameron at least have the experience in Europe's top leagues to not be baited into critical mistakes and their strong play in the tournament provides some room for optimism. 

The two sides will square off at NRG Stadium in Houston Tuesday night.