The Olympic tournament doesn't start for another month and the half, but we are already well-situated to make some extremely educated guesses about the roster. The keeper and forward situations look completely settled. And while there is some doubt over who will win the backup center back spot, there isn't all that much at stake in that question. Emily Sonnett and Whitney Engen likely care a great deal about who is selected and who is made an alternate, but there isn't much difference in their styles or qualities. Both are solid and would be strong replacements for the starters should the occasion arise.

The midfield, though, is a different story. Here, there are still serious debates, not just about who to bring but also about where and how they should play.

To kick things off, let's start by dividing the players into two groups: surefire locks to make the 18 (Carli Lloyd, Morgan Brian, Lindsey Horan, and Tobin Heath) and question marks (Allie Long, Megan Rapinoe, Sam Mewis, and Heather O'Reilly) from which Ellis will select one or two players. We'll cover each of these players below, but before getting into them, it's important to spend some time talking about the system they'll be using, since that informs much of the ensuing discussion.

4-2-3-1 or 4-5-1...or is it a 4-3-3? Or wait, a 4-2-4??

In the recent Japan friendlies, the stated formation was a 4-3-3, with Alex Morgan at the tip of the spear, flanked by two wider attacking players, and backed by a three-person midfield. In previous matches this year, though, they deployed something closer to a standard 4-2-3-1, with two holding players in the double pivot.

However, while these are different formations, the practical effect is often smaller than you might expect. In both cases, the goal is fluidity. That 4-3-3 can easily turn into a 4-4-2, with an attacking midfielder sliding forward and the forward wingers falling back. Or, just as commonly, they remain forward producing something closer to an old fashioned 4-2-4.

In fact, that de facto 4-2-4 is where the different approaches tend to meet. Regardless of setup, the same themes tend to repeat, with attackers launching forward and two players sitting further back to occupy the central midfield. Moreover, given the strong emphasis on attacking fullbacks, this often means five or six players pushed way up the field, with the center backs and holding midfielders sitting well behind them.

It's a high-risk, high-reward strategy. When everything clicks, the movement rips open spaces in the defense, allowing forwards to drift back and shuttle the ball up, while deeper-lying players can make runs through the resulting gaps. At their best, the US attack is almost unplayable because of all these interchanges and movement. But, by the same token, this sort of strategy is also difficult to keep under control. If too many players move forward at once, they risk emptying out the space in between the attack and defense, stranding the remaining holding midfielders. In those cases, play grinds play to a halt, forcing risky low-probability diagonal balls to escape pressure, and risking the loss of possession. On the rare occasions when the US looks second-best (examples: their first match against Japan last week, their match against France at the She Believes Cup), it's usually because the midfield has come unglued in this fashion.

On balance, the benefits of this approach are probably worth the risks. But it does generate real issues, and helps to frame some of the lingering questions for the midfield going forward.

Central midfielders

Given the above comments, the quality of play in the center of the pitch is often what makes or breaks this team. And that is particularly true when it comes to Morgan Brian, the heart of the midfield, who is quickly making a case as one of the best players in the world. Her skill on the ball is superb, and her vision of the field even better. Her tireless work in the middle of the pitch is the engine that drives the rest of the team, keeps possession alive, and ensures that the delicate balance of the midfield is maintained. When healthy, she's a close to a sure thing as you can get. Like Becky Sauerbrunn behind her, she rarely makes flashy plays, but that's because she's so preternaturally aware of the field and the run of play that she can cut off angles before they appear, intercept throughballs easily, and provide endless outlet balls for teammates under pressure.

Still, there are two big questions with Brian. First, while she excels in a true holding role—where her defensive talents can shine and she can provide relief against high pressure—this also risks sacrificing her creative talents. It should be possible for the two holding players to shift roles, one staying back and the other playing more as a box-to-box midfielder—but in practice the results have been spotty. The second problem is simpler, and hopefully more temporary. Brian has been nursing a lingering hamstring injury for two months, which has clearly affected her quickness and endurance. That shouldn't be a problem by August, though it wasn't supposed to last this long either.

Along with Brian, Jill Ellis is likely to play an additional central player. For much of this year, that's been Lindsey Horan, and that's likely still the best bet going forward. Horan has shown excellent talent going forward with the Thorns this year, which suggests a rough division of labor, with Brian as a 6 and Horan as an 8, that can theoretically maximize the value from both. That said, results have been mixed on that project to date, so that formation is by no means set in stone.

Two other options could also fill these spaces: Allie Long and Sam Mewis. Both are most comfortable in an attacking position, but they each also have experience with a more holding role. On current form, Mewis would seem to be the more obvious choice, since she has arguably been one of the best players in the NWSL thus far. However, Long started both of the Japan friendlies, suggesting that Ellis sees things differently. And while Long didn't always look entirely comfortable in those games (particularly the first), she likely acquitted herself well enough to solidify her hold on to the spot. If this is ultimately a competition between the two for one spot, Long likely has a marginal advantage in terms of versatility. Mewis is generally better as a rampaging attacking midfielder, but is a bit weaker defensively. And given that neither is likely to start, Long's greater experience might make her a more capable backup for a variety of potential roles.

Farther forward, at the heart of the attack, you'll find the sometimes-frustrating, sometimes-brilliant, always-intense Carli Lloyd. We're all familiar at this point with what Lloyd can bring to the table: excellent goal-scoring ability, incredible focus, and a desire to roam the field to a degree that defies straightforward positional description. This is one of the main peculiarities of the US ‘system' as described above - its persistent lack of a true number 10. Lloyd brings so much to the table that it's easy to understand why her inclusion is so automatic. At the same time, the tactical boxes that she tends to create also make it easy to understand why so many fans get frustrated with her stranglehold on the position.

The wings

To a certain extent, we got a test of what a Lloyd-less future might look like in the recent friendlies. With Lloyd out from an MCL injury, a few alternatives got a look—Mallory Pugh in the first match and Christen Press in the second. As with Lloyd, neither really played in a traditional number 10 role, though both theoretically occupied that rough field position. But there were interesting differences in their play. Pugh prefers to drift to the sides and make diagonal attacking runs, while Press tends to play as more of a true striker, somewhat withdrawn, but easily swapping with Morgan. Both Pugh and Press could fill this role again if necessary, but chances are high that Lloyd will occupy this spot absent additional injuries. That means that Pugh is far more likely to play where she has spent most of 2016: on the wing. Press has also been pushed to the right regularly, not her strongest position by any stretch, in an effort to get her considerable talents into the match. The same has also been true of Crystal Dunn, who has performed very well in a wide right position recently. One of these three is likely to cover the right in Rio.

On the left, the likeliest choice is Tobin Heath, who has been superb in 2016, both for the national team and in the NWSL—where she is on the short list for player of the year so far. She is immensely talented on the ball, and has really flexed her creative muscles this year, overcoming a history of frustrating inconsistency. Even acknowledging her relatively unsettled play in the two recent Japan friendlies, she's one of the clear form players on the squad right now.

This compares to her primary potential competition on the left wing: Megan Rapinoe. Well-known for her considerable contributions to the team last year, Rapinoe has been out rehabbing an ACL injury for all of 2016. However, she appears committed to getting back on the field within the next month. The question is whether a rushed return will really give her enough time to demonstrate a true return to form, not to mention the endurance needed for a grueling Olympic schedule. That said, Rapinoe offers a set of talents otherwise missing from the squad: world-class crossing ability, skill on set pieces, the instincts of a true winger. If I had to bet, I'd say Rapinoe makes the final 18, even if that doesn't translate to an automatic return to the starting XI.

On the other side of the field, one might make similar arguments for the inclusion of Heather O'Reilly. The longtime stalwart has earned hundreds of caps, and has speed, presence, and stability to offer on the right side of the midfield. But given her extremely limited minutes in 2016, it seems that Ellis has decided to move on. If Rapinoe isn't fit, I wouldn't be shocked to see O'Reilly take the final spot in the 18, but at this point it doesn't seem particularly likely.

What's the state of our nation?

Based on the evidence of the last few months, it's possible to make some educated guesses about the midfield. Jill Ellis is not a fan of changing horses in midstream, so going forward things will probably look much like they have in recent games. Still, some questions remain on a number of fronts. Will Dunn or Press will get the call on the right, or will it be Pugh? Will Rapinoe will show enough to re-take her spot on the left? Has Long done enough to play her way into the XI? And, more broadly, could a different formation entirely get more out of these players?

At this point, I see the trio of Brian, Horan, and Lloyd starting, with Heath and Pugh flanking them in the attack. And I'd bank on Long and Rapinoe as the final two names on the squad sheet. But there's good reasons to doubt any number of those guesses.

Who do you think will be starting in Rio, and who will make the squad? Who should be going? And how would you set them up? Give us your takes in the comments.