By Tzvi Machlin U.S. soccer fans and Borussia Dortmund fans got a huge scare yesterday when star midfielder Gio Reyna left a game after less than half an hour with an injury. Fortunately, the diagnosis is better than the injury looked. Reyna got his first start in nearly six months against Borussia Monchengladbach yesterday. But he went down after 27 minutes with a leg injury and looked distraught while being helped off the pitch. On Monday, Dortmund revealed that the injury was not serious. The team said that Reyna is expected to return to training in just two weeks. That should be enough tim…