Funny as it might be, the decision over who starts at left-back will likely have a lot to do with what Klinsmann does at the forward position. With five eligible forwards on the roster, and many of them fighting for a roster spot on the World Cup team, it seems unlikely Klinsmann will stick with the 4-2-3-1 formation he has used over the past year. In order to look at his forwards, the coach is more likely to go back to the 4-1-3-2 the U.S. used in the semifinal round of World Cup qualifying.
That could force Clint Dempsey to the left mid position which would, in turn, force Fabian Johnson into the left-back position. Johnson is more than capable in the back, despite the fact that Klinsmann has shown a preference to using him in the midfield. Of course, Johnson's last three games in the Bundesliga have been at right-back, so Klinsmann could throw everyone a curveball and play him there instead.