SAN FRANCISCO – Jurgen Klinsmann doesn't talk about it much but when he does you can tell it hurts.

The topic is the United States' "lost generation" of soccer talent, a glitch in the system that can be blamed in part for setting the country back in its quest for World Cup success.

Part of Klinsmann's blueprint when he took over as U.S. head coach in 2011 was based on a conveyor belt masterplan whereby emerging players would grow accustomed to the New American Way while coming through the youth ranks.

That process starts at the earliest age group levels but is supposed to feed directly into the men's team  for the Olympic Games, which is restricted to players aged 23 or under.

However, in a catastrophic campaign that saw a loss to Canada and a calamitous draw against El Salvador when goalkeeper Sean Johnson committed a late blunder, the young U.S. squad failed to make it to the 2012 Olympics in London.

Since, and according to Klinsmann, as a result of that setback, a wave of future hopefuls that seemed in line to be fast-tracked into the national team have seen their careers stall. Of the group, only Mix Diskerud, who scored for the U.S. in its first World Cup sendoff game – a 2-0 victory over Azerbaijan on Tuesday – is going to Brazil.

"[Diskerud] is coming from a group of guys that we had real trouble with getting to the next level, and I mean our Olympic team that was supposed to go to London," Klinsmann said. "There were a few guys, very special players coming with that team, and for whatever reason it just didn't work out the way it should have worked out.

"We lost a few on that path that should actually be part of this group now, this inner-circle group. All these very talented kids, they fell in a hole, a deep one.

"Because of what happened there, we desperately now from the senior level look at that generation and we want them to come through and we want them to grow into the senior team and they struggled with that because of that huge disappointment."

It seems strange to think it now, but back in early 2012 it was widely thought that as many as nine of the U-23s congregated at Nashville for the CONCACAF regional Olympic qualifying tournament could end up at the 2014 World Cup.

Diskerud was one of the standouts, but far from the only one. Terrence Boyd was a force at the top of the attack, while Joe Corona showed pace and energy. Those two were the only members, apart from Diskerud, to make the 30-man preliminary World Cup roster, but they were cut, along with Landon Donovan and four others, when Klinsmann pared down to 23 players.

Other forwards like Juan Agudelo and Teal Bunbury also then seemed to be in with a shot at becoming regulars with the men's team. Bill Hamid and Johnson were seen as being contenders for the No. 3 goalkeeper slot for Brazil, while Brek Shea's marauding runs down the left seemed indicative of a bright future.

Even Freddy Adu still seemed like a strong prospect at that point, captaining the under-23s and showing more than an occasional glimpse of the extraordinary promise he showed as a teenager.

Yet since the despair of that night in Nashville, nothing much has gone right for them. Shea couldn't break through when moving to EPL side Stoke City, spent a few unremarkable months on loan at second-tier Barnsley, and may now be poised to return to Major League Soccer.

Neither Agudelo nor Bunbury have blossomed to the extent that U.S. fans would have liked, Hamid and Johnson are still well behind U.S. men's third-choice goalkeeper Nick Rimando in terms of quality, and Adu is currently without a club following a disappointing spell at Bahia in Brazil.

Disappointment sometimes breeds resiliency, but in many cases, it just breeds more disappointment.

"You grow a lot from certain experiences, and definitely one like that, because that was a goal in my life to reach the Olympics," said Diskerud, who has continued to develop his game and could be a wildcard to make an impact this summer. "Another goal was to reach the World Cup, so now I am part of that."

Klinsmann just wishes that a few more of Diskerud's old pals had come through the ranks to join him.