Matt Besler and Geoff Cameron might hear it from every angle if they were paying any attention or had a moment's spare time. They could be reminded every day that this is the first time since 1990 the U.S. heads to a World Cup with no central defenders with previous minutes in soccer's showcase event.

And that makes an already daunting task in Group G much more challenging for the Americans, who face Ghana, Portugal and Germany next month in Brazil.

The competition for spots on the Americans' back line is fierce.

Nobody knows how the foursome will look for the team's World Cup opener June 16, yet Klinsmann will get a glimpse during an exhibition against Azerbaijan on Tuesday at Candlestick Park. He has choices for each defensive spot.