Schalke 04 midfielder Leon Goretzka has been ruled out of Germany&rsquo;s semifinal showdown against Nigeria at the Rio Olympic Games on Wednesday. <br /><br />The 21-year-old suffered a shoulder injury in their opening match against Mexico, and has returned home to continue his rehabilitation. <br /><br />&nbsp;Germany U23 coach Horst Hrubesch has told the official website of the German <span id="article-text"><span class="article-prime"><span class="articleLocatio</span>n">Football Federation that he won</span></span></span>&rsquo;t be calling up a replacement for his injured skipper, so he is now left with 17 players. <br /><br />Leonardo Bittencourt ( FC K&ouml;ln), Sebastian Kerk, Christian G&uuml;nter (both SC Freiburg) and goalkeeper Eric Oelschl&auml;gel (SV Werder Bremen) are the players on Germany&rsquo;s&nbsp; alternate roster for the Games. <br /><br />Nigeria coach Samson Siasia is sweating on the fitness of top scorer Oghenekaro Etebo ahead of the clash in Sao Paulo.<br /><br />Igho Kingsley <br />