USMNT's back line suddenly looks formidable ahead of Copa America

One of the biggest areas of concern for Jurgen Klinsmann has been his back four. It seems like every match the United States play in they have a different lineup of defenders hoping to keep the ball out of the net.

Heading into the Copa America Centenario, many thought it would be more of the same. Klinsmann scrambling to mix and match players to assemble a patchwork back line like he has for much of the past two years. However, after two friendlies against respectable opposition, we suddenly have a much clearer picture of who will line up across the back line for the USMNT.

Even though the same back four that shut out the No. 12 ranked team in the world didn't start together against Bolivia, we have a general sense of what to expect. In both of those friendlies the USMNT kept clean sheets. Was the back line perfect in either of those matches? No. But they sure did look way more competent in those two matches than they have in quite some time.

Chemistry and form certainly play a large part in how well the USA defense will hold up. It all starts with John Brooks in the middle. The 23-year-old German-American is undoubtedly the most talented defender the national team has. He's been tabbed as the future at center back ever since he committed to the team when he was 20 years old. He's finally living up to his potential and translating the form that he's exhibited with his club to the national team. He's primed for a huge summer while being asked to play a pivotal role for this team.

If Geoff Cameron can stay healthy, it's likely he'll partner the younger Brooks in central defense. This was the back line combo in the final friendly against Bolivia. Aside from one moment where the the center backs got stretched and allowed a giant hole to open up for a Bolivian attacker, it was smooth sailing against a decent South American team.

At the fullback spots we're likely to see DeAndre Yedlin on the right and Fabian Johnson on the left. Yedlin is coming off of a successful second half of the season for Sunderland and his confidence is sky high. He's been stellar for the USMNT at the right back position for four straight matches now. The speedster's defensive awareness has improved dramatically over the past year. He's become a complete defender instead of a pacey player who relies on his speed to recover.

Klinsmann's decision to play Johnson on the back line has been an opinion-splitting one. Some love the decision because it opens up a spot in the midfield to add another talented player into the mix. Others hate it because it pushes one of (if not the) best players into defense where his attacking abilities are somewhat negated. In reality, both of those arguments are right. The fact is, having Johnson at left back has solidified the back line and given an opportunity to another attacker to show his worth to the team. Whether you like it or not, it's the way forward for the Copa America.

All of a sudden, the USMNT defense, what looked like an extreme weakness for this team, as turned into one of its strengths in a matter of a few friendlies. There are still glaring chinks in the armor such as the depth behind these four players. If any of the four pick up an injury it could fall apart fast. But, if they can manage to stay on the field and continue to develop some chemistry it could be the first semblance of cohesive defensive unit for the USMNT that we've seen for a long time.

We're not claiming to have a crystal ball, but using logical conclusions, it's safe to assume this will be your back four against Colombia on Friday. Unless of course Klinsmann decides to change everything up at the last second and try something completely new and different. Then we're back at square one, scratching our heads.