Who's going to Rio: USWNT defenders

Last year at the 2015 Women's World Cup, the WNT defense kept the United States in it long enough for the offense to start clicking and bagging goals. That back line of Meghan Klingenberg, Julie Johnston, Becky Sauerbrunn, and Ali Krieger seemed impenetrable, imperturbable, unbothered by attempts to get through to Hope Solo.

That defense has shown some cracks in 2016, but there still aren't too many questions of the back line going into the Olympics. The primary big question is whether Kelley O'Hara or Ali  Krieger will start, while the secondary and somewhat less important question is who will go as the third center back.

Krieger or O'Hara?

Most of the 2015 back line is still intact ahead of Rio with one crucial difference: Ali Krieger seems to have lost her starting spot to Kelley O'Hara.

In the last 12 games, O'Hara has gotten nearly twice the minutes that Krieger has gotten, 723 to Krieger's 390. O'Hara has also picked up more starts, eight out of 12 and two subs, while Krieger has started four games and subbed in for five.

Ellis clearly likes O'Hara's versatility since she can be switched from right to left at a moment's notice (or can even get shifted to forward in a pinch) and has been doing just that when she subs Klingenberg for Krieger. Krieger tucks into her accustomed right back spot and O'Hara shifts over left.

If we look at available NWSL stats, even though Krieger has stats logged for five games vs O'Hara's six logged games, Krieger still has 28 interceptions to O'Hara's 15 and makes them at a rate over twice what O'Hara does. She also has more recovers/90 and clearances/90. Krieger beats O'Hara at pass completion percentage, with Krieger at 74% and O'Hara at 68%, and at her forward pass completion percentage, with 68% for Krieger to 61% for O'Hara.

On the flip side, over seven games O'Hara has 17 shots and five shots on goal while Ali Krieger has four shots and two SOG, both over the same minutes played. O'Hara attempts about four crosses per game while Krieger attempts a little over two crosses per game. So we can see that O'Hara is the more attacking player, which probably leads to more risk from her and lower defensive stats, while Krieger will certainly work up the wing, but tends to stay at home more and be more positionally aware.

Engen or Sonnett?

Neither one of them has particularly gotten minutes of late, meaning Ellis will be making her decision based on camp performance and, possibly, NWSL performance. Engen and Sonnett play for two very different teams; Engen is with bottom-of-the-table Boston Breakers and Sonnett is with third-place Portland Thorns, just one point behind the top two teams. Engen also sometimes plays in a five-back for Boston, while Sonnett stays in a more traditional four-back.

Once again limited stats are available for NWSL, but from the beginning of the season, Engen tends to make almost twice as many blocks per 90 as Sonnett, and over three times as many clearances per 90. Part of this can be attributed to Portland being stronger all over the field, which requires Engen to go into defensive action more often. They also have similar pass completion percentages and distribute the ball in just about the same proportion directionally. Sonnett has slightly more aggressive stats in terms of interceptions, take ons, and disrupting possession. Engen stays at home more, required to be a true anchor for a weaker team, while Sonnett can push back a little more without creating the same risk.

The wedge that really seems to be dividing them here is experience. Engen is 28 and has 35 caps and four goals for the national team. Sonnett is 22 and has nine caps. At this point, Engen is the more reliable backup defender. But Ellis has also stated plenty of times that she needs to start preparing this team for a turnover in the roster, so that new talent has time to mature for the 2019 World Cup. Perhaps that means Sonnett, assuming that Ellis sees her as someone who will last out the next cycle. Going into a World Cup already having experienced the hectic, compressed schedule and expectations of a major tournament could make a meaningful difference.

On the other hand, there is some pressure on Ellis to win back-to-back major tournaments, something no women's soccer team has accomplished yet. Ellis may want to go with the familiar option here, and then really dig into Sonnett or whoever she has her eye on in the central defender pool in the two years before the next World Cup.

Common wisdom has Ellis taking only six defenders on an 18-person roster, and honestly, burning a midfield or forward spot in order to bring four center backs is not exactly the height of wisdom. So: the locks are Becky Sauerbrunn, Julie Johnston, Meghan Klingenberg, Ali Krieger, and Kelley O'Hara. There's just Engen or Sonnett for filling in a sixth defensive spot. What wins, experience or development?

If history is any indicator, Ellis will take Engen for one last tournament, preferring security to getting Sonnett some big-game exposure. Let us know in the comments if you think Ellis will surprise us at all with her defensive picks.