I read somewhere on one of the internet’s dependables that Mexico’s back line is looking pleasantly settled ahead of this weekend’s Rose Bowl biggie. Must be nice. The United States’ back line is … well … let’s go with “ongoing work in progress.” Settled? If it were any “less settled” it would be a fidgety 5-year-old on a sugar high. In 16 matches of 2015, US manager Jurgen Klinsmann has used 13 different combinations along the back line.

So who gets their turn in the churn Saturday as the US meets Mexico outside Los Angeles, with a place in the 2017 Confederations Cup on the line? Only Klinsmann knows. Except that, given the state of ongoing flux, even he can’t be assured of his own choices to face El Tri.

Here’s a quick snapshot of the ongoing disquiet in the US rear guard:

The team’s preferred left back got his first cap in pre-9/11 America. DaMarcus Beasley is 33, so not exactly “over the hill” just yet, and he’s still performing quite well for the Houston Dynamo. None of that is the issue. Rather, it’s that he keeps trying to retire, only to have Klinsmann lure him back. Such is the telling need.

SEE MORE: Jurgen Klinsmann vs. Tuca Ferretti is a battle between 2 different coaching philosophies.

The preferred right back, Fabian Johnson, is a solid choice. But he is naturally left-footed and therefore better as a left back. Even better is Johnson deployed in midfield. But such is the need.

Johnson looks fully recovered from an August calf injury. While that’s great news ahead of Saturday’s clash, consider this: With Brek Shea out of the picture for now, with Graham Zusi’s form weaving in and out like an agility dog through poles and with Alejandro Bedoya playing interior positions so frequently in a US shirt, we could make a good argument that Johnson is the team’s best threat to provide natural midfield width. Which would be great – except that he’s needed at outside back due to a concerning lack of other options.

SEE MORE: Mexico’s defense looks surprisingly settled.

So the situation at outside back is somewhat stable, although this thin layer of security has been achieved more or less through temporary fixes. Mark that down as “less than ideal.” Still, it’s a picture of enduring steadfastness compared to the situation at center back, which really is a complete mess.

One of last year’s World Cup starters (Matt Besler) has fallen alarmingly low on the depth chart. Then again, at least he is on the current roster! Not so with Omar Gonzalez, who has been “just OK” in Major League Soccer this year. That may be good enough against San Jose or Sporting KC, or someone else in league play. But to put some “just OK” on the field against a motivated bunch of Mexican attackers is really asking for it. Klinsmann doesn’t currently adjudge the longtime Galaxy man to be one of his best eight defenders of the moment.

So his choices at center include Ventura Alvarado, the Club América man who has been consistently underwhelming on the national team and is not starting regularly in Liga MX, or Besler, who wasn’t playing well enough in the summer, apparently, to be on Klinsmann’s Gold Cup roster.

Or Tim Ream, whom Klinsmann has never seemed to favor, even though he’s the best defender in the player pool for passing smoothly out of the back, the very way Klinsmann himself prefers. (Yes, that one remains a head-scratcher.) Or Brad Evans, who is far more likely to play on the outside, although he has generally been used as a converted center back this year for Seattle.

Klinsmann’s best choice at center back looks like Geoff Cameron, starting at the position now for Stoke City. Thing is, Klinsmann has always looked at Cameron and seen “outside back” or even a “holding midfielder.” He has typically leaned away from Cameron as center back.

Answers have hardly been forthcoming, even as Klinsmann has deployed six different center backs at some point over the last four matches, including that latest alarm bell clunker, a 4-1 loss to Brazil.

Ordinarily, this would be a reasonable time for tinker-dinker in all areas. We are still in the comfy zone, a period before World Cup qualifying gets serious. Yes, Russia 2018 qualifying commences next month for the United States. But the competition in the upcoming round looks soft as high quality tissue paper. Klinsmann could drag Thomas Dooley out of retirement and install him along the back line and the United States could still probably advance into the final round of the CONCACAF process.

But the timing here became tricky and problematic when the United States stumbled so badly at the Gold Cup, setting up Saturday’s one-off for all the Confeds Cup marbles. Mercifully for the United States, Giovani dos Santos is injured, so he won’t be available to dice up the United States the way he did in the very same Rose Bowl four years back (during the Gold Cup final, a loss that ultimately cost Bob Bradley his job). Still, Mexico has enough offense to make life difficult on Brad Guzan or Tim Howard, the choices to keep U.S. goal before a sold-out crowd inside the historic ground.

SEE MORE: Why I’ll be watching USA vs. Mexico on FOX, not Univision.

The temptation may be to blame Klinsmann for not assembling a more trustworthy, consistent rear guard. While developing a competent back line is a priority order for any manager at any level, Klinsmann’s defenders in the pool haven’t exactly stepped up and seize the moment, now have they? The reality is that personnel must do its part, too; no one has put a grimacing, unyielding stranglehold on any of the positions.

(Well, Beasley has … but he is practically begging “let me go!” And Johnson is fine, although he’s needed elsewhere.)

Michael Orozco, John Brooks, Alvarado and plenty of others have moved off and on the back line, mostly with results ranging from “not bad” to “needs work.” (Brooks continues to struggle with an injury and wasn’t named to the current roster.)

You know what the United States back line needs? It needs Carlos Bocanegra. Not actually Bocanegra himself, of course. But a presence like the former US captain, who earned 110 caps not so much for his speed or raw ability. Rather, he was a back line marshal, a cop on the beat who directed traffic and kept the law and order.

It’s what Klinsmann has always wanted from a figure like Gonzalez, who has more physical ability on his worst day than Bocanegra had on his best. Or it’s what Klinsmann wants from Besler, who reads the game with aplomb and is certainly dedicated, but who is such a nice, swell fellow that perhaps he doesn’t have the requisite bark and bite of a commanding back line general.

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So Klinsmann’s back line looks like a classic “conundrum,” defined more generally as the choice between equally unappealing options. In this case, his options aren’t so much “unappealing” as they are “unconvincing.”

No matter, though. He’s got to get this one right. Then, this chosen foursome has 90 minutes to accomplish something we haven’t seen since Brazil ’14, a year and change back: the United States put together a cohesive, commanding, locked-in 90 minutes against a worthy attack.